This manual will introduce you to the operation and installation of the Zeron 800. For many of you, this will be your second (or even third or fourth) Zeron. The 880 has many new features. Less useful ones from prior models have been removed while others have been improved. Although you may be familiar with some of this manuals sections, re-read them all carefully. Many contain small but important changes. (What happens with reversed power leads is but one example). When you thoroughly understand how your 880 operates, you will be able to adapt these instructions to fit local rally customs. However, please do write or call concerning any questions or problems you may have.

Practice on an old event before your first real competition. The old rally, rerun without the pressure of staying on time, will confirm your understanding of the 880.


The 880 uses integrated circuits which may be damaged by static electricity, i.e., the kind which shocks you after walking across a rug on a dry day. If you must remove the 880 from its case, hold it by the front panel and try not to touch the printed circuit boards or their components. Don't worry if you accidentally contact a part. It's not likely that any harm was done.

Mounting studs are located on the top of the case. Refer to the illustrations at the end of the manual for their placement. If you intend to use the 880 on performance rallies, the case should be supported along the bottom so that the mounting screws do not take all the stress. The 880 will slide out of its case when the screws in the corners of the front panel are removed.

The heatsink, which protrudes from the back of the case, is connected to the +12 volts side of the car's electrical system at all times. Be positive that it cannot touch the car's chassis or other metal parts connected to the chassis. This won't hurt the 880, but it will blow the fuse and shut you down! The heatsink, as you might imagine, gets hot. It won't hurt the car, but you wouldn't want to reach behind the case and touch it.

The 880 is built with components whose operating temperature range is 32 to 160 degrees Fahrenheit. Operation outside of these values may cause incorrect calculations. On hot days when the car is parked in direct sunlight, the temperature on the dash may exceed the upper limit. Watch out for this at breaks and rest stops. Turning off the displays will keep the 880 from overheating if you must leave the car in a poor location. When the 880 is left unattended for a long time during a winter rally, leave the displays on. They'll keep the circuits warm even when the temperature is below freezing.


The 880 will operate from either of two sender types. The cable driven unit is designed for permanent mounting between the speedometer and its drive cable. The magnetic unit uses magnets attached to the car's wheel that pass by a sensor as the wheel rotates. Unless you run performance rallies or TSD events with a large percentage of unpaved roads, there is no advantage in using either one or the other. The magnetic sensor needs an hour or two for installation (and some mechanical ability) while the cable type is relatively quick to install. When wheel slippage can become significant, the magnetic sender will overcome it without the need for vulnerable outside cables and wheel gears.

Disconnect the cable from behind the speedometer. Attach the sending unit to the back of the speedometer, then reconnect the cable. The short square pin included with the unit goes between the speedometer and the sending unit. When the car is moving, the cable should turn evenly without binding or making noise. A small amount of speedometer needle bounce at low speeds is normal; large fluctuations indicate a binding cable. Check for any sharp bends you may have caused in the cable. You might also try either changing the position of the cable or rotating the sender on the back of the speedometer.

On a small number of cars, it is very difficult to get the sender directly behind the speedometer. In some cases, a short extension cable can be inserted between the sender and the speedometer. At other times, it may be necessary to cut the speedometer cable and have adaptor fittings installed. If your car is one of the problem few, we'll let you know. We can help in either case.

The cable unit can also be run from an un-driven wheel cable or from an auxiliary cable connected to the speedometer cable via a 1:1 tee gear. In both of these situations, ignition noise will be picked up on the sending unit cable and may cause false inputs to the 880. GROUND THE SENDING UNIT BY RUNNING A SHORT WIRE BETWEEN IT AND THE CAR'S CHASSIS. THIS IS VERY IMPORTANT. Nearly every problem reported as sending unit trouble can be traced back to failing to perform this one simple step.

When driving the sending unit from a separate cable, do not over lubricate the inner core. The core needs only a light coating of grease for proper operation. When the cable is packed with grease, the excess may work its way into the sender and block the sensor. This also holds true for the speedometer cable in your car if it ever needs replacement. Don't do anything to it. The factory sends it ready for installation.

The sending unit is not weatherproof and may become inoperable if exposed to rain, mud, etc. Always try to mount it in the passenger compartment or in the trunk. If you must mount it out with the engine, wrap and seal a plastic "baggie" around it. Obviously, the sender and its cable should be kept away from hot engine parts. Taping the sender and a dead wheel cable to the outside of the car is asking for trouble. The first rain shower will soak everything.

The sending unit comes equipped with the proper fittings to mate with the speedometer in your car. If you change cars, they can be replaced or exchanged to fit the new rally vehicle (see price list). When you change the fittings yourself, it may be necessary to adjust the small washers located on the sending unit's rotor. The bent washers place a slight drag on the rotor and prevent false outputs during vibrations. Increase or decrease the drag by bending the washer(s) until the rotor offers a slight resistance when turned by the square drive pin. Check the drag about every 20,000 miles. A diagram of the sending unit's parts and assembly is found at the end of the manual.

Most cars use speedometer cables whose ends terminate with a 0.106" square pin. Some French and British cars use a 0.118" pin. The rotor in your sending unit will accept the pin size in your car. When you switch to a car requiring the other size rotor, a new one can be ordered from the manual's price list.

Because of the large variety of cars and equal number of individual preferences, the installation of this sender can only be covered in general terms. Common sense demands that all work done under your car be performed with the car supported by jack stands. Once the magnets are in place on the wheels, use extreme caution when the wheels are spin balanced. An improperly attached magnet could fly off.

Refer to the drawings at the end of the manual for outline dimensions of the sender parts and general mounting layouts. Two small brackets are included to help in mounting and alignment. The body of the sensor is completely threaded to also aid in alignment. The final decision on where and how to mount the sensor is up to you. All brackets should be short and sturdy to eliminate false outputs from a vibrating sensor. For obvious reasons, the bracket should move with the wheel assembly when attached to a front wheel. Don't mount to a single piston disc brake caliper. The caliper shifts as the brake pads wear down. Also, never mount the bracket to a McPherson strut tube. Significant flexing can occur during hard driving and could cause the magnets to hit the sensor.

Loop the sensor cable so that it is protected from rocks and has plenty of room to flex. Strapping the cable to the back of the brake fluid line is a good way to lead it into the car. To help route the cable, several nylon strips (called cable ties) are included with the sender. pass the strip around the cable and securing point, insert the small end through the other end, then pull up snug. To protect the cable, the rubber grommets found on the cable should be inserted into any holes you had to drill in the car's sheet metal. It's usually easier to run the sensor FROM the Zeron rather than the other way. Drilled holes need only clear the sensor, not the larger connector.

Once you have the sensor mounted to the car, adjust it and the magnets so they pass about 1/8" from each other. Don't epoxy the magnets until the brackets are set. During the alignment period, the magnets will hold themselves to steel wheels. Tape them to other type wheels. Setting the gap at less than 1/8" WILL NOT improve the sensor's operation. In fact, it only degrades some of the sensor's special electrical characteristics. In addition, a very small gap may result in magnet/sensor contact during severe roads conditions.

The sensor requires two magnets mounted to the inside (not the rim) of the wheel. Space them equally for balance. These magnets have been specifically designed for this application. Other magnets will not work correctly. Do not attempt to use smaller magnets. Although other magnets may work at low speeds, as the car's speed increases, the Zeron's electronics may reject as noise a pulse whose width is too short. For more stringent installations on stage rally cars, smaller magnets can be used so long as they can be attached to a shorter (slower) turning radius. Contact Zeronics for advice and magnets.

Five magnets and a two part epoxy come with the sender. The magnets are very strong and may snap out of your hand when held next to each other or ferrous metal. The magnet could split if this happens. The superior magnetic strength of the magnets allows for non-critical alignment between sensor and magnets. Additional magnets can be ordered from the manual's price list.

Use two magnets for the wheel on the car, and two for the spare tire. THE MAGNET FACE MARKED WITH THE RED DOT IS THE FACE WHICH MUST PASS THE SENSOR. Mount each magnet so that this entire face passes the end of the sensor. After the preliminary magnet/sensor alignment, carefully remove the wheel from the car without disturbing the magnets. Mount the spare tire, adjust the magnets on it, then remove the spare.

Mix the epoxy according to the directions on the tubes and then allow it to set for 24 hours once it's applied. Be sure that the wheel is free of dirt and oil. Without bumping the magnets, completely coat ALL sides with epoxy. This will form a box around each magnet and keep it from working loose. Next, build up the epoxy on each side except the sensing surface. Spread the epoxy out so that it has a large bonding area on the wheel. This epoxy has been field tested with many other types. When used correctly, it can only be removed by hammer and chisel.

The magnetic sender will operate at temperatures from -40 to +300 degrees F. It is also waterproof and will continue to operate even if submerged in water. If you run rallies where ice and slush are common, you might use a little caution during rest breaks. Because the magnets and sensor are relatively close together, an ice bridge might form between them when you stop. Though it's not likely that you would pull the sensor off center when you leave, being overcautious won't hurt. It's possible to leave the car parked with them separated if you mark the magnet locations on the outside of the wheel.


A pre-wired power cord is included with your 880. Connect the red wire to +12 volts (uninterrupted by the ignition switch) and the black wire to ground. Attach the leads securely. Just a momentary power loss (either +12 volts or ground) will erase the data in the 880. Do not select a positive lead from under the dash. It may contain numerous slip-on connections as it is routed from point to point. Your best tap point is at the fuse holder where the main power lead enters. If there are no screw terminals in the holder, strip back the power lead's insulation and attach the red wire there. Solder and then wrap with electrical tape for a secure joint. Attach the ground lead (black) under a screw in the car's metal chassis. Scrape away any paint which might cause a poor electrical path. To use a loose fitting cigarette lighter plug for power is inviting disaster during a rally.

You will notice that the power connector has four pins instead of only two. The pins are wired in pairs, two for +12 volts and two for ground. If your installation must use additional connectors, continue using this idea. It's another precaution against a brief power loss.

A 3 or 4 amp fuse is located in the +12 volts lead of the power cord. NEVER RUN YOUR 880 WITHOUT THIS FUSE IN PLACE. It's your protection against shorting the heatsink or reversing the power cord polarity. Without the fuse, the cable from the back of the 880 could melt and the 880's electronics could be damaged. A spare fuse is taped to the back of the 880. In the unlikely event that another fuse is needed, it can be found at most gas stations, electronic supply stores and TV repair shops. Under desperate circumstances, a fuse from your car may work. Take one from the fuse holder that runs an un-needed circuit (radio, fan, etc.).

After you have completed your power connections, plug in the 880 and see if it will turn on. If the leads were reversed during installation, the fuse will blow. THIS TEST SHOULD NEVER BE PERFORMED WITH THE SENDING UNIT PLUGGED INTO THE 880. It puts a direct short between +12 volts and ground that bypasses the fuse.

Keep the sending unit and power connector pins free from dirt and grime. Never wrap masking tape around the pins. You may use tape to hold the connectors together if you feel they might separate.

The 880 will operate on input voltages of 7 to 20. Go below 7 volts and data may drop out of the 880's electronics. Your car's output voltage normally varies between 10 volts when starting the engine and 14 volts when charging. A good battery is your best protection against having the voltage drop below 7 volts.

While a car's nominal output voltage is 12-14 volts, electrical noise and large voltage spikes may occur at the same time. The 880 has built-in safeguards to isolate itself from this type of noise (from fans, lights, etc.). THE ONE EXCEPTION IS SOLID IGNITION WIRES. While few cars come with these wires as standard equipment (Alfa's are one), if your car has them, they need replacement with ordinary carbon resistance wire. Don't forget the wire between the coil and distributor.

Porsches and newer Alfa's (both use solid wires) are equipped with suppressors to eliminate ignition noise. New wires are not reqUired. If you feel that solid wires are absolutely necessary on your car, use a shielded type. It's available at some auto supply stores.

Don't be tempted to "see what happens" before deciding to replace solid wires. Sometimes, hours of close observation may indicate that all is well. Don't be misled by this apparent lack of trouble. Ignition noise can be extremely elusive. It may only appear under hard acceleration or on damp days. Since the noise is picked up on the sending unit cable, the 880's calculations will be in error. Why risk getting bad checkpoint scores?

For night rallies, you can order a small gooseneck light from the manual's price list. The light has a pre-wired plug, spare bulb, and ON/OFF switch. Two mounting holes are located on the top of the 880's case and a power jack is provided on the rear panel. Do not use the jack for other electrical connections since it only has a small load capability.


Your 880 is run by a small computer which begins its program when the 880 is first turned on. The displays will come on at 00.00, a computer correction factor of 400 will be put into the 880's memory and the buzzer will sound for a short time. All this will indicate that the 880 has just come up from a power off condition. If they occur during your shakedown drives, a faulty power connection must be found and eliminated. Occasionally, defective power connections will be indicated by random patterns of digits and blanks in the 880's displays. Always switch the 880 off and start it up in normal fashion. Then find the bad connection. You will never have a problem of this type if you use a little care in making the power attachments.


The intensity of the 880's displays is controlled by the switch on the left of the front panel. Use BRT (bright) for daytime rallying, DIM for night events, and OFF to turn off the displays.


The Odometer records official rally miles from 00. 00 to 99.99 in increments of 0.01 mile (kilometer). Once the 880 is corrected at the end of the odometer calibration leg, the Odometer will match the rally's official mileage. The count direction, up or down, is controlled by a switch you'll read about later. To zero the Odometer, press the small button to the left of the display while also pressing the button on the lower right of the front panel. The second button, referred to as the "safety" from now on, has several purposes. One of them is to keep you from accidentally zeroing the Odometer. Because it must be pressed along with the other button, an unintentional bump on the zeroing button won't cause the loss of your mileage.

The lower display on the driver's readout also shows mileage. Normally it runs along with the Odometer and gives the driver official mileage. However, when the zeroing button next to the Odometer is pressed (without the safety), the mileage clears from the driver's odometer and an incremental count begins at 0.00 miles. Only three digits are used. That indicates an interval mileage is being displayed. Use this feature for pauses over a distance, a short free zone, actions keyed to a mileage interval after a clue, etc. When the zero button is pressed a second time, the display returns to the Odometer's official mileage. The driver's odometer automatically starts at official mileage when the 880's Odometer is zeroed.

Directly below the Odometer are three small thumbwheel switches. The buzzer will sound when a mileage set in the switches is equaled be the Odometer. Any mileage from 00.0 to 99.9 miles can be chosen. The alarm system is always on. You can't forget to arm the system after a new mileage is set in. The buzzer turns off by itself after about 2 seconds. When another mileage is entered, the buzzer will sound when the new distance is attained. If the mileage re-occurs after a mileage zero point or during a return from being off course, the buzzer will go off again.

The alarm system sets to the nearest 0.1 mile. You won't want the buzzer going off at the exact mileage with which you're concerned. Use a mileage slightly prior to that point to give yourself time to prepare for the required action. When you don't need the alarm, dial in a large mileage which will, in effect, turn off the system.


The Clock display shows time-of-day from 00.00 to 59.99 minutes. At the beginning of each new hour it starts over at 00.00. You cannot accidentally zero, stop or set the Clock. These adjustments are discussed later in the manual. The Clock display is also used to show other pieces of information. When you want to view the 880's correction factor, it will be displayed here. Actions such as pauses and gains will have their amounts indicated in this display when they are entered into the 880.


The time calculated by the 880 (based on speeds and distance) is recorded in the Computed Time Counter (CTC). The count is in decimal minutes from 00.00 to 59.99 with automatic rollover to the next hour. The count direction is controlled by the same switch as the Odometer and will be covered later on. To zero the CTC, you must have the large rotary switch turned to PARK and then press the button next to the Clock and the safety. Because of the way your 880 operates, you will rarely, if ever, need to zero the CTC during a rally. Consequently, the zeroing sequence will prevent an unintentional clearing of the CTC. In fact, unless you are demonstrating the 880 or using it to run leg times for your own rally, you will never find it necessary to zero the CTC.

Actions keyed to time intervals after a clue are done by noting the time in the CTC at the clue, then adding the interval to that time. When the CTC reads the total time, execute the required action.


The upper display on the driver's readout indicates the computed time error. This is the difference between the Clock and CTC. As will be illustrated later in the sample rally, you will rally on a time-of-day basis. That is, when you are "on time", the time in the CTC will be the same as the time in the Clock. When the times diverge, the differential displays the error. The ten minute position is dropped to make viewing less complicated.

Examples of what you might see displayed are:

                   12 -- 0.12 minute ahead ["up"]
                    1 -- 0.01 minute ahead
                    0 -- on time
                  999 -- 0.01 minute late ["down"]
                  972 -- 0.28 minute late

As you can see, the readout drops below 0 when you are late. The advantage lies in eliminating the necessity for a + or - indicator. As you gain experience, you'll find that driving a little "up" is the most effective tactic for getting good scores. Most of your time will be spent at 2 to 5 on the readout. These numbers will always mean that you are ahead. It won't be necessary to continually associate the extra piece of data (the + or -) each time you glance at the readout.

When you're really late, mental arithmetic usually won't be necessary. For example, you're delayed by traffic and the differential reads 861 when you check it. You'd now be more concerned with getting back on time, not being exactly 1.39 minutes late.

The table below illustrates the CLOCK/CTC/DIFFERENTIAL relationship:

                  CLOCK    CTC      DIFFERENTIAL

                  00.25    00.25      0  [on time]
                  01.25    00.25    900  [1 minute late]
                  01.25    02.00     75  [0.75 early]
                  12.34    12.40      6  [0.06 early]
                  12.34    21.34    90E  [9 minutes early]
                  12.34    22.34    00E  [10 minutes early]

Note that an "E" has appeared in the later examples. The "E" tells you that the CTC and Clock are more than 5 minutes apart. Without the "E" in the sixth example, you might have thought you were rallying "on time" when in fact you were actually ten minutes early. You must always insure that the CTC and Clock are in the same ten minute period. Once you're up and going in the rally, there's no chance of getting out of this window without knowing it. However, you should compare the counters at the end of the odometer calibration leg, at the end of transit zones, when you recover from being off course, etc. If the "E" is there, you're in the wrong window. Once the "E" appears, it stays constant while the other 2 digits behave normally.

You will soon notice that the differential does not display each the CTC and Clock count. If the car is stopped, the readout counts steadily downward as the Clock counts up. Once you are up to rally speed, the readout will hold a constant value even though the CTC and Clock are not counting at the exact same moment. There's no distraction from digits flipping up and down. This steady number system is achieved by updating the differential once every 0.01 minute. Because of this, you may occasionally see the display skip numbers when you go faster than the assigned rally speed. It only means that several CTC pulses were received during the 0.01 minute update interval.

The driver can also use the differential for pauses and gains. Suppose the route instructions call for a pause while the navigator is busy. For a 0.25 minute pause, slow the car until the differential drops to 975 (0.25 minute late). Continue with 975 as the "on time" reference until the navigator can enter the pause as usual.


Rally speeds are entered in miles per hour (kilometers per hour) with the thumbwheel switches on the top right of the 880. The computer correction factor corrects the entire computer, therefore the speeds you enter are the ones given in the route instructions. Any speed from 1.0 to 99.9 mph (kph) in 0.1 mph steps can be used. Speeds less than 1.0 mph calculate as zero mph. The tenths thumbwheel switches are red to distinguish them from the other positions.

The toggle switch between the two banks selects the active bank. The unused bank can then be preset to the next rally speed. For small repetitive speed changes, it's OK to change the active speed while the car is moving. For unexpected or forgotten speeds, set the inactive bank and then throw the switch.

Avoid using extremely slow speeds whenever possible. The measuring accuracy of the 880 may hurt your score. The following instructions were taken from an actual event.

                  34.45     21. "STOP". Change average speed to 1 mph.

                  34.92     22. "MAX". Change average speed to 35 mph.

The calculated time for this distance is 28.20 minutes. The rallymaster used it to give the crews a break at a gas station which occurred between the mileages. When the course was measured, the mileages were rounded off to the nearest 0.01 mile. Since you were given two hard mileages, the time of 28.20 for running that distance is correct. However, the 880 calculates using pulses received every 3-4 feet. Had the actual distance been 0.474 miles, the 880 would compute a time of 28.44 minutes. That's a 0.24 minute error at the next checkpoint. You should treat this problem as a 28.20 minute transit zone. No reasonable rallymaster would expect you to maintain speeds this low. He would expect you to be able to calculate the elapsed time given the speed and distance.


This control locks (splits) the data displayed in the Odometer, Clock and CTC whenever it is thrown to "checkpoint". (The driver displays are not affected.) The counters continue to record new data, but the additional information is not shown until the switch is turned off. Throw the switch at checkpoints or when you want to hold data so that you can write it down. At checkpoints, the mileage to the line, your time-of-day arrival and your computed arrival time will be split in the displays. When you are mistimed, the Clock will verify the time-in you wish.

If you are mistimed, the checkpoint captain's first statement after your protest will usually imply that your clock is in error. You can verify the Clock's accuracy without losing the split information. Push the button next to the Clock. Real time-of-day will return for comparison with the workers time piece. Releasing the button brings back the original split.


This rotary switch selects the 880's operating mode. The 880 is off when the switch is in the PWR OFF position.

DIST. ONLY (Distance Only) and D.O. REV. (Distance Only Reverse): -- These modes are used when computed time is not required, e.g., during an odometer calibration leg or transit zone. The Odometer and driver readout both record distance, but no computed time is registered in the CTC. As will be explained shortly, you are not prevented from adjusting the CTC with the add/subtract pushbuttons. This allows you to set the CTC while running the odometer calibration leg or to add in a transit zone time as you complete the distance.

ON COURSE: -- This is the normal operating mode for the 880. Both Odometer and CTC count forward. Decimal points are turned on between all of the display digits to indicate when the Mode Control switch is not in this position.

OFF COURSE: -- Both Odometer and CTC are reversed. Since the differential follows the CTC, it also reverses. Use this mode to retrace the rally course after a course following error or to back up to check a clue.

PARK: -- This position turns off the 880's speed and distance functions. Neither mileage nor time from the sending unit are allowed into the counters. The add/subtract pulse circuits still operate as usual. Use this mode whenever you wish to leave the rally course (during a break, etc.). The blank positions are also PARK. Overshooting one of the other positions won't turn the 880 off or put it into TEST.

The PARK mode also comes in handy when you are turning around from an off course excursion. As you pass a tree, sign or other clue, switch to PARK. U-turn at the first opportunity and switch to OFF COURSE as you pass the landmark from the other direction. This procedure keeps the guess work out of where to reverse the 880 as you turn around. Switch directly to ON COURSE when you regain the rally route.

TEST: -- This mode activates an internal pulse generator to run the 880 as if it were in a moving car. You can test or demonstrate the computer with TEST. With a computer correction factor of 1333, the 880 behaves as if it's in a car going 60 mph.

When TEST is used, remember the "car" traveling at 60 mph. If the active speed bank has 30 mph in it, the differential will indicate that you are getting more earlier all the time. When you double the correction factor mentioned above, the 880 will think it's in a car going 120 mph (2 miles a minute).

MPH PARK: -- This position stops the 880's speed calculations and causes the 880 to internally store the distance traveled while in MPH PARK. You can remain in MPH PARK for 9.999 miles although you clearly would not want to. When you switch out of MPH PARK (to any position), the 880 takes the current active speed, computes the proper time for the distance stored internally, then ADDS this time to the CTC. To avoid confusing situations, MPH PARK can only be used when you are on course and want the deferred time added to the CTC. You can't "lose" time when you switch directly from DIST ONLY to ON COURSE or vice versa. Even when a mileage pulse occurs while you are momentarily in MPH PARK.

Here are some possible ways to use MPH PARK: A rally requires that you change speed to 20 mph whenever you turn onto an unpaved road. When you turn onto the road unexpectedly, switch to MPH PARK. Dial 20 mph into the active speed bank at the first chance you have, then switch back to ON COURSE. The 880 will think that you actually made the speed change at the turn.

As a second example: You pass a clue for a speed change but note that it is attached to a disabled school bus. Can you or can't you use a clue attached to a vehicle? You could stop, pull out your rally regs as the driver watches the differential sink, then leave after making a decision. A better way is to switch to MPH PARK and let the driver continue along the course at about rally speed while the decision is being made. Should the sign not be allowed, turn back to ON COURSE. The CTC (and differential) will update as if nothing ever happened. Had the sign been legitimate, dial the new speed into the active bank before switching back to ON COURSE.

When you make an incorrect speed change, MPH PARK allows you to back out the error and correct it. This will be covered in greater detail later on.


The +T, -T, +D, and -D positions are used with the .01, .10, and 1.00 pushbuttons to pause, gain, add or subtract computed time, and add or subtract mileage. The rotary switch selects the type of pulse, the pushbuttons, the amount. This system has been employed on the three preceding Zeron computer series and has proven to be the most effective way to quickly and simply adjust the different functions of the computer. A system using a bank of thumbwheel switches might require setting then unsetting up to 4 switches just to add 0.01 mile to your Odometer at a given point. Entries to a keyboard in a bouncing car are difficult and must be backed up by a monitor to verify correct key stroking. Zerons have none of these disadvantages.

For example, to enter a pause of 1.20 minutes, turn the switch to +T (for + time), then press the 1.00 button once and the .10 button twice. If the pause were given in seconds, you need to convert to minutes and hundredths.

When you enter a pause (+T) or gain (-T) the amount goes into the CTC while the entries from the pushbuttons are indicated in the Clock display. In the previous example, as soon as you had pressed the 1.00 button, the Clock display would have gone to 1.00, then 1.10 after the first .10 push, and finally 1.20 after the second .10 push. Only 3 digits are displayed to distinguish these numbers from the usual time-of-day. When the pause has been entered and checked, push the button next to the Clock to clear the display and return it to time-of-day. Most pauses and gains can easily be performed in 3 or 4 seconds.

Since pauses and gains are nothing more than the addition or subtraction of computed time, you can use +T and -T whenever you need to set the CTC to a specific time. For example, you'll need to set the CTC to your time out from the end of the odometer calibration leg. Suppose this time was 48.00 minutes. Assuming the CTC is at 00.00, switch to -T and subtract 12 minutes by pushing the 1.00 button 12 times. You'll do the same thing at checkpoints, the end points of transit zones, and at time of day restarts.

+D (+DISTANCE) and -D (-DISTANCE) adjust Odometer mileage. They do not change the driver's odometer when it is running incrementally. Use these positions to correct the Odometer when needed.

The add/subtract features outlined above or in subsequent paragraphs are not affected by the car, i.e., you can be moving or stopped. The 880 just adds or subtracts the amounts you've entered to its other computations.

Always keep the rotary switch in the +T position until it's needed for another action. You'll find that you rarely do more than pause a few times while rallying between checkpoints. All the decimal points come on to remind you when you're not switched to +T.

Pulses add or subtract as directed by the Pulse Control switch. The Mode Control does not affect them. When you're in OFF COURSE, pulses add or subtract as usual. A pause entered while rallying off course would require a gain to remove it on the way back to the proper route.

+CALC, -CALC, +C/M, and -C/M are tied into the 880's computed time circuits. They also can be used whether or not the car is in motion. An example will show you how these functions operate.

Let's assume that you switch to +C/M (+CALC/MILES), the car is stopped, the active speed is 40 mph, and the 880's counter's contain the following data. Now push the .10 button twice.

                          Before         After
          Odometer        34.00          34.20
          Clock           time-of-day     0.20
          CTC             15.00          15.30

As you can see, the pushbuttons are tied to distance while the speed circuits generate the corresponding time for the mileage entered (0.20 mile at 40 mph yields 0.30 minute). It's as if the rally car traveled 0.20 miles almost instantaneously. The information in the counters is exactly the same as it would be had you driven the 0.20 miles on the road. Once again the Clock keeps track of your entries.

CALC is the same as C/M but without the mileage added to the Odometer. The Odometer in the previous example would not have changed to 34.20 but would have remained at 34.00. The +CALC and -CALC positions are used primarily on rallies where timing is done from timing line to timing line. (See the sample rally.)

A typical on-course use of the calc modes follows: You have just come to a stop sign at the end of a long unpaved road. The route instructions give the mileage to the sign as 23.89. Your 880 has 23.86. (The rallymaster had more wheel slippage during course measurement then you have on rally day.) You must now correct both mileage and computed time. The CTC is low because your mileage is too short. Had the rally speed been 30 mph, the CTC would be 0.06 minutes lower than it should be. (0.03 mile at 30 mph is 0.06 minutes.) You could correct the errors by adding time and mileage separately using +T and +D. You would also need to calculate the amount of time to be entered. By using +C/M, all it takes is three pushes on the .01 button.

Suppose the mileage in the preceding example had been given for a clue which occurred while you were at rally speed. In this case, you would note the mileage error, turn to +C/M, then press the .01 button the correct number of times. There's no need to stop the car.

For more detailed information on the calc modes, refer to the section on calculating elapsed times for you own rallies.

Two positions remain on the Pulse Control switch. The one marked as CAS causes the mileage for the last speed change to appear in the Odometer. The Clock and CTC blank out to avoid any possible confusion. If you discover that you made the last speed change incorrectly, you'll have the exact mileage for it. Now you can use two of the 880's other features to correct the error. Here's how.

Switch to MPH PARK and note your mileage. Find the incorrect speed change mileage by looking at CAS. Let's say the difference is 1.70 miles. Turn to -CALC and back out 1.70 miles at the incorrect speed (the speed is still in the active bank). Enter the correct speed and use +CALC to add back the correct time for the 1.70 miles. The error is now fixed. Turn out of MPH PARK so that the CTC can update and give the driver (who has been continuing along the rally course) his exact error on the differential.

To make this operation even easier, you might try this. Look back at CAS first. Let's say the mileage indicated is 24.79. Now check the Odometer which reads 26.68. Continue at the wrong speed until 26.79 miles, then switch to MPH PARK. The wrong speed was entered exactly 2.00 miles ago and is easily figured. Of course, the driver should be trying to get close to the proper time as the navigator makes the corrections. When the incorrect speed is too slow, you know you are late and should increase your speed immediately.

The final position (straight down) enables the third rotary switch. This is the only way any of the functions on that switch can be used. You can never accidentally alter the Clock's time-of-day or change the computer's correction factor unless those functions are first turned on by this position.


The Clock is set by using the CLOCK positions on the remaining rotary switch. Although this switch is not active unless turned on by the Pulse Control rotary switch, it's best to leave the knob pointing to a blank position until you need one of the functions. There's no such thing as being too careful during a rally!

To zero the Clock, turn to HOLD/ZERO and press the 1.00 button. To stop the Clock, use the .01 button. (The buttons are noted by the lettering on the front panel.) To add time, turn to SET and use the pushbuttons to add in the amount needed.

The quickest method for setting the Clock to time-of-day is: Just prior to an even minute on your time reference, zero the Clock and keep it at 00.00 by continuing to press the 1.00 button. When the even minute arrives, release the button. The first time count will occur exactly 0.01 minute later. Next, switch to SET and use the 1.00 button to run the minutes up to the correct time. That's all there is to it.

When you use WWV or CHU radio signals to set the Clock, it's often hard to anticipate the first beep after the verbal announcement. Here's a simple trick to help set the Clock perfectly. Don't let the Clock start on the even minute. Continue holding it stopped until the 6th beep (sixth second), then release it. The beeps come at regular intervals and are easy to predict. The Clock is now six seconds (0.10 minute) behind, so turn to SET, press .10 once, then run up the minutes.


The computer correction factor adjusts the sending unit input pulses to allow the 880 to run at official rally miles. The factor is stored inside the 880 and displayed (in CLOCK) whenever you are in +FACTOR, -FACTOR, or F/CALC (Factor Calc). (You can peek at the factor just by pressing the button next to the Clock.) The factor is changed by using the pushbuttons and +FACTOR or -FACTOR. Remember, you must activate these positions from the Pulse Control switch. The 880 can calculate a new correction factor for you. That procedure follows this explanation of correction factor basics.

The equation for adjusting your factor at the end of the odometer calibration leg is:

                                  OFFICIAL MILES
                     NEW FACTOR = -------------- X OLD FACTOR
                                  COMPUTER MILES

Example: Your factor at the start of the odometer calibration leg is 4200. The leg is 14.92 miles long and the 880's Odometer reads 15.07 at the end point. 4158 is your new correction factor.

                                 ----- X 4200 = 4158

Before running your first event with the 880, you may want to establish a base correction factor (BCF). This factor will run the 880 at statute miles in your car. Once obtained, make a habit of starting each rally with it. This will normally keep you within a few percent of the rally's official mileage and thus make the odometer calibration leg easier to run. Remember that a correction factor of 4000 is loaded into the 880 when it is first turned on.

To find the BCF for your car, it will be necessary to run the 880 against a known statute distance. Many highways have mileage markers posted along the edge. Or, perhaps an old rally measured in statute miles can be partially rerun. When a suitable course is not available, lay one out using your car's odometer. A more precise BCF can be developed when the opportunity arises.

Once you've selected a course (at least 5 miles or more), set in a factor of 4000 and run it. Use the formula to calculate your BCF. A rerun using the new factor will find your Odometer mileage equal to the course's "official" length. You may find your BCF easier to remember if you round off to an approximate value (4600, 4200, etc.).

Occasionally, you may want to adjust the factor during the rally. You might need to do this if it started to rain. Small changes can be mentally calculated with very little trouble. For each 0.01 mile you wish to change your mileage in 10 miles, change the factor by the value of its first digit. Increase the factor to increase mileage, decrease it for less. Suppose you wanted to increase your mileage by 0.01 mile in 10 miles and your factor is 4100. Adjust the factor to 4104 (4100 + 4). To illustrate again, your factor is 4850 and you need a decrease of 0.02 mile per 10 miles. Change the factor to 4840 (4850 -4.8 -4.8).

When you know the number of revolutions per mile at the input of the sending unit, you can compute your BCF from the formula below. A little math will tell you that the 880 needs a minimum of 400 revolutions per mile. Most cars have between 800 and 1600. None are lower. BCF's for un-driven wheels depend on wheel diameter and vary between 800 and 1000. The vast majority of cars have speedometer cables which turn at 1000 revolutions per mile. The BCF's in these cases would all be around 4000. The factor has been designed so that it will not normally go much above 5000. This gives the 880 sufficient range to run in kilometers. (1.00 kilometer = 0.62 mile... old factor times 1.61). Of course, speeds are now entered in KPH, not MPH.

                   CORRECTION FACTOR = --------------------
                                       Revolutions per mile


Here are the steps involved:

Dial the official mileage at the end of the odometer calibration leg into the four left most speed switches. The other two switches and the bank selector switch are not important. Some examples of how the banks would look are:

                                 Mileage     Speed Banks
                                  12.34        123  4xx
                                   9.54        095  4xx

Notice that the "decimal point" has stayed in the same relative position between the ones and the tenths digits on the left bank.

Switch to F/CALC and push the .01 button. The new factor is immediately computed and entered into the 880's memory. The official mileage at the end of the leg is put into the Odometer.

Although you can't see it, the 880 measures distance to the nearest 0.001 mile. When a factor calculation is made, that mileage is rounded to the closest 0.01 mile. That is, if the Odometer reads 12.64 at the end of the leg, the 880 will use 12.65 if the actual mileage is 12.645 or greater. The maximum error when allowing the 880 to perform the math is 1/2 count. Depending on the size of your factor, that's about 0.01 mile error in 80 miles. It's too small to even worry about. When you make a mistake that will force the factor above 9999, the buzzer will sound when you press .01 and no computation will take place. The information printed an the front panel next to F/CALC will remind you about how the 880 is set up.


You already know about using the safety to zero the Odometer and CTC. Another of its functions is to clear out the 880's internal counting registers each time the button is pressed. This will help you get better scores. Why? Imagine that you are at a checkpoint's out-marker and are preparing for the next leg. When you pull away to clear the area for other cars, you notice that the CTC and Odometer count within the first few feet. What causes this to happen? As mentioned before, your 880 measures in 0.001 mile steps. While you might only see 12.89 at an out-marker, the 880 could really have 12.899. If the rallymaster gives the mileage as 12.89, you're going to have 12.90 just passed that point. A push on the safety sets the 880 to 12.890 miles. As will be explained in the section about computing elapsed times for your own rallies, the CTC works somewhat like the Odometer in that other information is stored out of sight. The safety push also gets rid of that data.

Use the safety at the start and finish of the odometer calibration leg and whenever you feel that the rallymaster is starting his calculations with a clean slate. When you zero the Odometer, the safety is also pushed. You automatically clear out the internal registers.


Install the 880. Check that it is working correctly and that you have all your equipment before you leave home. Let's assume the following:

      1. The first car leaves the start at 8:01:00 am.
      2. Your car number is 13.
      3. Your BCF is 4100.
      4. The general instructions require a speed change to 35 mph whenever
         rally mileage is a multiple of 22.00 miles (22, 44, etc.).

Turn on the 880 about 30 minutes prior to your starting time (8:13:00). Set the Clock and enter your BCF. The remaining time can be spent checking your other equipment and going over the general instructions one final time.

      00.00  1. Begin odometer calibration leg at "HOD". Zero your
                odometer. Take 30 minutes to reach instruction #8.

Check your Odometer to see that it is zeroed and that you are in DIST ONLY, then leave "HOD". As the driver follows the instructions to #8, the navigator should set the CTC to the time they are due to leave the end of the odometer calibration leg (43.00). Next, the speed banks would be set up for the factor calculation (115 2xx).

      11.52  8. End calibration leg at "Chip". Leave this point at
                8:30.00 plus your car number in minutes. Begin 40.

Stop at instruction #8 and record your mileage. Let's call it 11.41. Use factor calc to compute the new factor (4140). The new factor and official mileage are put into the 880 when you press the .01 button. Enter the first rally speed (40), switch to ON COURSE and then pull ahead to clear the sign for other cars. The CTC will begin counting up based on 40 mph. Pull off the road (assuming you were given adequate time to run the leg) and wait for time-of-day (Clock) to catch up to the CTC's time. The differential will indicate the time remaining. As it nears 0, get the car up to rally speed.

If you want to calculate the factor for yourself, follow these steps. During the calibration leg, set the CTC to 43.00 and enter the first rally speed. At the end of the leg, record the mileage, set the Odometer to 11.52 miles, switch to ON COURSE, then pull ahead. Your new factor is not in yet, but a short distance at the old one won't matter. Calculate and enter the new factor. The 880 is ready for the first leg. Leave when Clock catches up to CTC.

Throw the checkpoint switch as you cross the timing line. Compare the Clock's time with the one assigned to you by the workers. Straighten out any discrepancy before you turn off the switch. When everything is taken care of, pull up to the out-marker. Correct your Odometer if necessary.

Most rallies will use one of two common methods to start you on the next leg. The first type has the checkpoint zone as dead mileage, i.e., timing is from out-marker to checkpoint timing line. The 880 handles this very simply. At the out-marker, set the CTC to your assigned time out, then pull slightly ahead to clear the marker for other cars. The differential will indicate the time left before you start the next leg. Get the car up to rally speed as it nears 0.

When you pulled ahead in the above example (and at the end of the odometer calibration leg), the CTC and Odometer began to count up. This is what should happen. The counters are merely giving you the data to the point where the car is parked.

The second checkpoint method uses timing from checkpoint line to checkpoint line (no dead mileage). In this case, the time from the checkpoint line to the out-marker must be added to your assigned time-out. Let's imagine that your assigned out time is 9:15.00, the rally speed is 40, and you are now at an out-marker 0.12 mile from the checkpoint line. As in the prior example, you would check your mileage then set the CTC to 15.00. Next, switch to +CALC and add in 0.12 mile of computed time at 40 mph. The CTC will go to 15.18 and you can now pull ahead to wait for the differential to count down to 0.

In both of the above cases, the CTC can be set to your time out in just a few seconds. Why? Because it is reading only a few minutes less than your assigned time out. (It has the time to the checkpoint line plus a little for driving up to the out-marker.)

If you plan to use the safety to clear out the 880's internal registers, press it before using +CALC. pushing it afterwards may clear out data that truly belongs in the CTC's internal registers. When you read the section concerning elapsed times you'll see why.

      21.90 miles ---  the buzzer will sound because you put 21.9
                       in the alarm system at the beginning of the
                       rally (didn't you?). Enter 35 mph in the
                       inactive bank in preparation for the speed
                       change at 22.00 miles. Dial in 43.9 (or the
                       next important mileage).

      28.36  23. "FOP". Begin transit zone of 20 minutes to the
                        next instruction.

      28.90  24. "VA REEL". End transit zone. Begin 40 mph.

At 28.36 miles, switch to DIST ONLY and note the time in the CTC. During the transit zone, add 20 minutes to the CTC. Plan to arrive at instruction #24 before your time is up. At "VA REEL", set in the new speed, turn to ON COURSE and then pull ahead to wait out the balance of your time. Be sure that the Clock and CTC are in the same 10 minute window when you leave (no "E").


The ability of your 880 to precisely measure mileage is much greater than you will need during a rally. When your factor falls in the 4000 to 5000 range, you can correct the 880 to read within plus or minus 0.01 mile in about 80 miles. Considering that you and the rallymaster are measuring on different days, in different cars with different drivers, about the best you can expect is to be within 0.01 mile after 15 to 20 rally miles. All things considered (including a little luck), your sores should average about 0.01 minute error per checkpoint.

The Clock will stay within 0.01 minute during an all day event. Extreme temperature fluctuations may slightly affect its accuracy. Even in these cases, the Clock will not vary by more than 0.02 minute per 24 hours.

The 880 has been constructed to withstand all the usual rally jolts and bounces. Its design is the product of 7 previous generations of Zerons. Not a single mechanical problem has ever been reported on any of the last 3 Zeron series. However, it won't hurt to use some common sense in mounting your Zeron for stage rallying. Don't mount the case rigidly to the car's frame. This will only transfer every shock taken by the car to the 880. A little care applied in mounting your computer will insure many years of trouble free rallying.

Although your 880 is built only with quality components, there is always the possibility it could stop functioning correctly. Before sending the unit back, write or call Zeronics and describe the malfunction. In many cases it may not be necessary to return the unit. Most major parts are mounted in sockets for easy removal and replacement. This feature is standard on all Zeron products. It makes for quick and inexpensive repair of any problem you might have.


While the 880 can handle many of a rally's math problems for you, some knowledge of the basics might save you when the going gets tough. The math most often found in rallies involves the elements of time, speed and distance. It is usually easier to work in minutes per mile factors (MPM) than in miles per hour.

For those not familiar with MPM factors, here's a short explanation. Basically, a MPM factor tells you how long (in minutes) it takes to run 1 mile at the assigned speed. The factor for 35 mph is 1.714. This means it takes 1.714 minutes to run one mile at 35 mph. You can mentally move the decimal point to get the times for 10 miles (17.14 minutes), 0.10 mile (0.17 minute), and 0.01 mile (0.017 minute... about 2 hundredths).

Missed speed changes can be "fudged" by using MPM factors. Suppose you forgot to make the speed change that was part of the last route instruction. You've been driving at 30 mph (2.000) instead of 35 mph (1.714). Unless you can risk returning to the execution point, you'll need an educated guess for the gain time required to correct the CTC. With MPM factors you can quickly see that it takes about 0.29 minute less to run a mile at 35 mph than it does at 30 mph. For each mile you've been at the wrong speed, a gain of 0.29 minutes is needed. If you estimate that distance as 1.5 miles, enter a gain of 0.44 minutes (1.5 X 0.29).

Two helpful formulas are:

                            60                               ELAPSED MINUTES
          MPM FACTOR = ----------               MPM FACTOR = ---------------
                       SPEED (mph)                           ELAPSED MILES


The following technique may be your best method for "zeroing" a checkpoint. You will quickly notice that once you are up to rally speed, it's a simple matter to hold the differential at 0. The readout will occasionally count down to 999 or up to 1 while the car's speed varies. If this happens just before you enter a checkpoint, you won't have time to react. Even when you can see the checkpoint in the distance, it's not possible to drive at the exact rally speed. The readout may still change right at the timing line.

As an alternative to driving at 0, try using 2 t o 3. When you see the checkpoint, drop below rally speed. The readout can only count down towards 0. With a little practice, you'll be able to hit 0 just before the timing line. When a checkpoint occurs without warning, a tap on the brakes will kill the extra time.

To improve accuracy of the differential's data, the 880 checks the CTC's internal registers just prior to computing your error each 0.01 minute. That data is rounded up or down to the nearest 0.01 minute in the calculation. When the update occurs, you can be sure that the differential is never more than 1/2 a hundredth in error.



When you put on your own rally, the C/M modes are very useful when calculating the official elapsed times (OETs). To understand how the 880 computes, recall the section in rally math that dealt with minutes per mile factors. Your 880 can be thought of as using MPM factors with 5 places to the right of the decimal (un-rounded). The factor for 35 mph is 1.71428.

To help you visualize what is happening, assume that the CTC has 5 more digits to the right of its decimal point. Also, since your 880 is actually running in thousandths of a mile, let's pretend that we can see that data also. Now, let's use +C/M and examine the following:

                                             ODOMETER    CTC
       Start (Speed bank at 35 mph)      00.00(0)      00.00(00000)
       After one push on .01 button      00.01(0)      00.01(71428)
       After another .01 push            00.02(0)      00.03(42856)
       After another 8 (or a single      00.10(0)      00.17(14280)
         push on .10 at start)
       After 9 more .10 entries          01.00(0)      01.71(42800)
       CHECKPOINT                        01.02(0)      01.74(85656)

                                   OET: 1.75 minutes

Notice that had you only been able to see the CTC's 4 normal digits, after 0.01 mile you might have thought that the time was just 0.01 minute. Since the 880 runs the rally course in thousandths of a mile, it's always accumulating this unseen data. Under actual rally conditions, the CTC would have turned over to 00.01 about halfway through the first 52 feet. Counts 2 and 3 would have occurred between the 0.01 and 0.02 mile points. This gives the CTC a smooth count rate though it might appear otherwise as you run OET's.

Once you reach the checkpoint mileage with your calculations, you must determine how to round off to obtain the OET. Dial 00.2 into the left speed bank. The next two lower CTC digits will appear in the differential display. In the above example, the differential will show 85. Now rounding is easy.

Think back to the explanation of the "Safety" button. Remember that one of its functions was to clear out the 880's internal registers? A push on the safety at the end of the preceding example would clear the CTC to 01.74(00000). Had there been any mileage in the Odometer's internal register, that would have also cleared to zero. Now you can understand what happened in the example of pulling ahead at a checkpoint and having the displays count immediately. To get your best checkpoint scores, you can see why it's important to clear them out before you start the next leg.

The first time you run OET's, try setting up the 880 this way: put 00.2 in the left bank and use only the right one for rally speeds. Turn the Mode Control to PARK. (This really doesn't make any difference, it's just that you'll be zeroing the CTC a lot.) In most cases, an OET calculation will begin with the Odometer set at the previous timing line's mileage (out-marker's mileage) and the CTC cleared to 00.00(00000). Enter pauses and gains at the appropriate places using +T and -T. Speed changes are made at the mileages you obtained during course measurement. With some thought, you will see how to enter other rally timing data (transit zones, etc.) to your OET's. It won't take more than a few minutes to run (and re-check) the OET's for a short event.

If you're so inclined, you can determine the maximum OET error that could result by using MPM factors not rounded in the 5th place. You'll find that it is always less than 0.01 minute per 1000 miles. At normal rally speeds, that's about 0.01 minute per 24 hours of rallying. Since the 880 uses the same calculating methods during an actual event, its accuracy is the same. Your chance of zeroing a checkpoint really depends upon accurate measurement, correct clocks, human reaction time, and a small dose of luck.


When you're a worker and not a competitor, the 880 can help you man a checkpoint. Not only will it time a single car, it can record and hold the times for up to 10 cars. To prepare the 880, enter a correction factor of 0000 (you'd obviously never use it while rallying), rotate the Pulse Control switch to some position other than straight down, then turn to PARK. All the other computer functions are disabled while you are in PARK. Unnecessary displays are blanked out to conserve the car's battery.

The 880 will now exhibit the following:

            ODOMETER ---- blank display
            CLOCK ------- time-of-day
            CTC --------- blank display

To time a car, push the 1.00 button. The car's "split" time will appear in the CTC and the number 1 will appear in Odometer. After you log in the time, press .01. Both Odometer and CTC will blank out again. If a second car had arrived just after the first one, press 1.00 again. The Odometer will go to 2, while the CTC remains split at the first car's time. Now when you press .01 to clear the split shown, the second car's time comes up in CTC and the Odometer drops to 1. After the second time is recorded, press .01 again to clear it.

The 880 can store up to 10 cars this way. When the tenth one is reached, the Odometer will read "FULL". Of course, with ten cars waiting at the checkpoint for their in-times, worrying that the 880 is "FULL" is the least of your problems.

The car arrival times are called up in the order in which you entered them. When several times are stored in the 880, it's best to call them up and record them all at once. Then, if a later car comes in while you're still busy with the first couple, the 880's memory will be empty. This should help simplify your log keeping chores.

To get out of the Multi-Split condition, switch out of PARK.


If you've ever been a rallymaster, you know there are times when you'll work on the course without someone else's help. The driver's odometer can help you quite a bit. Especially as the course takes shape. To make your work less prone to error, put 00.3 in the left speed bank. This will blank out the differential and leave only mileage displayed


Have you ever wanted to accurately calibrate your speedometer or have an indicator of your true speed during long trips to out of town rallies? Your 880 can give you this information. Enter 00.1 in the left speed bank and switch to DIST ONLY or DO REV. The car's speed will be displayed in place of differential. YOU MUST USE YOUR STATUTE MILE CORRECTION FACTOR OR THE SPEED WILL NOT BE ACCURATE. Only speeds above about 15 mph will be shown. The display will stay at 000 until you reach that rate. Speeds are given in whole numbers (48, 34, etc.) and are accurate to +/- 1/2 mph.

The 880 computes your average speed over a distance of about 75 feet, then displays it. Therefore, during rapid acceleration or deceleration, the speed shown will be below or above your true speed. Once you're at a reasonably steady speed, the mph indicated will be the car's actual speed.

When you lay out a rally, you might use this feature to help determine appropriate speeds on different sections of the course.


Using an 880 only for stage rallies would truly be a case of equipment overkill. However, should the spirit move you or should your normal rally schedule include both TSD and stage events, the 880 can run instruction interval mileages. Enter 00.4 in the left speed bank and 60.0 in the right bank (active). The CTC will become a second odometer. When the checkpoint switch is thrown, the CTC splits the current mileage, clears itself to zero while still holding the split time, then begins counting over again. When you switch out of checkpoint, the CTC's new mileage is displayed. In most cases, you'll just switch into and out of checkpoint to clear the CTC and start a new interval.


BCF for a 1000 revs per mile car: 4000

TEST Correction Factor for 60 mph: 1333

                        OFFICIAL MILES 
                        COMPUTER MILES

"E" in Differential: Out of 5 minute window

Driver Display Interval Mileage: Press Odometer button to start.
                                 Press again to return Official Mileage.

Clock display: Press button to view correction factor.
               Press button to recall time-of-day while in
               "checkpoint". No loss of original split.

All decimal points are on when not in ON COURSE or +T

Safety: Clears internal Odometer and CTC registers

MULTI-SPLIT CHECKPOINT TIMER: Correction factor -- 0000
                              Mode Control -- PARK

MILES PER HOUR (in differential): 00.1 in left speed bank.
                                  Mode Control -- Dist Only or DO REV

CTC LOWER REGISTER (in differential): 00.2 in left speed bank

BLANK OUT DIFFERENTIAL: 00.3 in left speed bank

INTERVAL MILEAGE IN CTC: 00.4 in left speed bank and 60.0
                         in right speed bank (active)


Zeronics warrants this product to be free from defects in workmanship and material for a period of one year from original date of purchase. our obligation under this warranty is limited solely to repairing or replacing, at our option, any part when the product is returned to us within the warranty period providing: (1) the defective unit is returned to us transportation prepaid by the purchaser, (2) no modification or change has been made to the unit's wiring or circuitry, (3) the unit has not been damaged by misuse, neglect, improper operation, accident, or alteration as determined by Zeronics. No other obligation is implied or expressed.


(Prices subject to change without notice)
All prices include shipping costs.

The following parts are available should you change rally cars or set up a second car.

For a fee of $10, you may return your cable sending unit and have the fittings exchanged to fit a different car. This offer is good only when the fittings removed from the sender are still in use on a currently produced car. In addition, the fittings must be in good condition and not marred, gouged or otherwise damaged. The old fittings will be kept by Zeronics and the replacements will be mounted on your sender. The complete unit will be inspected and the rotor drag adjusted to specifications.


Most basic features are same as previous Zerons (why change a good thing).

Price will definitely be under $700 and may go as low as $650 with a magnetic SU.

Size - volume about 60% of 550-770

Full time mileage on driver readout. ODOMETER mileage is normally displayed. When button next to ODOMETER is pressed, the readout mileage clears to 00.00 and counts from there (used for keeping track of a 2 mile free zone, pause over a distance, etc.). A second push on the button brings back official mileage. Readout automatically starts at official mileage when odo is zeroed. When mileage is running incrementally, 3 digits displayed.

Differential is back to 3 digits but is displayed a little differently, e.g., 1 down (999), on time ( 0), 2 up ( 2), 12 up ( 12).

Fully automatic mileage alarm (same as 800) to nearest 0.1 mile using the thumbwheels directly below the ODOMETER.

CLOCK display serves same function as "P/G" on old AUX counters in 550-770. When a pause or gain is entered, the CLOCK display immediately shows the amount, e.g., a .10 pause would make the display read 0.10. Pressing the button next to the CLOCK display clears the pause and returns it to time of day. 3 digits on P/G.

The correction factor is in memory and adjusts up or down using the pushbuttons and +FACTOR/-FACTOR. The factor is displayed in the clock when the rotary switch is in factor adjust positions or FACTOR CALC. If you just want to peek at the factor, press the button next to the clock and the factor will come up in the display.

Factor calc is much simpler than in the 770. Just dial official mileage into speed banks during the odo leg (xx.x x--), at finish, switch to FACTOR CALC and press .01. New factor is immediately calc'd and entered into the 880; official mileage is put into the ODOMETER. This system doesn't require any counters to be cleared or any special switch set up. You shouldn't need more than about 10 seconds at the end of the odo leg to get the 880 completely ready for the first leg. When the factor is calc'd, the unofficial mileage in the Odometer will automatically be rounded to the nearest .01 mile. That is, if the Odometer reads 12.16, the calculation will use 12.17 if the actual mileage is 12.165 or higher.

"CAS" will cause the mileage at the last speed change to display in ODOMETER. CLOCK and CTC will blank out to avoid confusion. (Think how yo could use this to store a mileage.)

When switches not in +T or ON COURSE, all decimal points come on (not on readout) and in driver mileage.

+CALC, -CALC, +CALC/M, and -CALC/M are similar to "CALC" and "CALC/M" on 770 but can now be used when the car is moving (easy adjustment of both mileage and computed time at a given official mileage). The 1.00 button enters even miles, not fast add as in 770. None of the minor problems outlined for the calc modes on the 770 apply. The 880 uses a slightly different computed time system than the older ZERONs. Under normal rally conditions it yields even more accurate OET's. Think of it as using a minute per mile factor (added or subtracted for each 0.001 mile) with 5 places to the right of the decimal point (un- rounded). It gives a maximum error of 0.01 minute in 1000.00 miles.

Throwing the checkpoint switch always Odometer, Clock, and CTC to split into the displays (e,g., you'd always get time of day in the Clock even if it had the factor displayed prior to throwing the switch. If the Clock button is pushed, actual time of day is again displayed in Clock (you can verify correct time at checkpoints). Split time returns when the button is released.

MPH PARK--Stops computed time but stores official distance traveled while in MPH PARK (up to 9.999 miles). When switched out of MPH PARK (to any other position), the 880 takes the current active speed, computes the time for the distance you were in MPH PARK, then adds it to the CTC. This system avoids any confusing operating situations by only allowing it to be used when you are on course and want computed time eventually for the distance traveled.

You won't miss any computed time if you need to switch to the distance only mode; even when a distance pulse occurs during MPH PARK as you switch from ON COURSE to DIST ONLY. The CTC will be corrected as you go from MPH PARK to DIST ONLY.

Possible uses are: (1) Automatic CAS when turning onto unpaved. As you make the turn switch to MPH PARK, dial in new speed when you can, then switch back to ON COURSE.

(2) You miss a CAS and estimate that it occurred about 1.7 miles back as you switch to MPH PARK. Turn to -CALC and remove 1.7 miles at the current (incorrect) speed. Dial in correct speed and use +CALC to put 1.7 miles back in with the proper computed time. When you switch out of MPH PARK the CTC will update and your CAS error will be corrected.

The 880 can run multiple splits when used as a checkpoint timer (same as 88). All unused displays are blanked out to conserve the car's battery.

To set up for it, enter a correction factor of 0000 then switch to PARK. Turn Pulse switch out of bottom position. The other two rotary switches are disabled as long as you stay in PARK. The 880 will display:

                                   (BLANK) 0



To time a car, push the 1.00 button. The split time will appear in the CTC while the Clock keeps on with normal counting. The number "1" will appear in the Odometer. If another car comes in, push 1.00 again. That split goes into memory behind the one shown in the CTC and the Odometer now reads "2". To recall splits (in order, of course), push .01. You can store up to 10 cars with the Odometer reading "FULL" when the 10th one is entered.

Speeds of 00.0 to 00.9 calc as zero MPH.

TEST factor = 1333.

BCF for 1000 Rev car is 4000.

Differential shows corrected MPH (above 20) with left bank at 00.1 and in DO or DO REV.

Differential shows lower CTC info with left bank at 00.2.

                                         00.00 (XX)
                                         CTC    In Differential

Alarm blows when powered up.

Push Safety and Clock button to clear CTC.

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