Zeron 700 ZERON-700
Rally Odometer/Clock


This manual will explain the installation and operation of your Zeron 700. A thorough understanding of how the 700 functions will help you adapt these instructions to local customs. It is recommended that you read this manual completely and then practice before competing in an event. An old rally, rerun without the pressure of staying on time, can check your mastery of the instrument.


The 700 utilizes an integrated circuit technology that is susceptible to damage from static electricity, e.g., the kind that shocks you after walking across a rug on a dry day. Therefore, several precautionary measures should be taken when you handle this unit. There is no danger of harming the 700 when the unit is in its case. If you must remove it, hold it by the front panel and avoid touching the printed circuit boards and their components. Even if you do accidentally contact a part, don't worry. It's very unlikely that any harm was done.

Mounting studs are located on the top and back of the case. Refer to the illustrations at the end of the manual should you find it necessary to drill more holes. If you intend to use the 700 on performance rallies, the case must be supported along the bottom so that the mounting screws do not take all the shocks and jolts (the case may crack). The 700 will slide out of the case after 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 700, but it will blow the fuse and shut you down! The heatsink, as you might imagine, gets hot. Not hot enough to harm your car, but it will surprise you if you reach behind the unit and touch it.

The 700 is built with components which operate at temperatures between -40 and +85 degrees Celsius. Operation outside this range may cause incorrect calculations. While you won't be rallying with the inside of your car at -40 degrees C, temperatures at the high end are possible under certain conditions. On hot days when the car is closed and in direct sunlight, temperatures on the dash may exceed the upper limit. Watch out for this at lunch breaks and rest stops. Turning off the displays will help keep the 700 from overheating if you must leave the car in a poor location. When the displays are off, the 700 draws a current of about 0.06 amp (instead of 1 amp). A weak battery will not be run down.

Sending Unit: The 700's sending unit is designed for permanent mounting between the car's speedometer and the cable driving it. Disconnect the cable from behind the speedometer, mount 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 strange noises. 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. It might also be helpful to change the position of the cable or to rotate the sending unit on the back of the speedometer.

On a small number of cars, it is very difficult to mount the sending unit directly behind the speedometer. In some cases, a short extension cable can be placed between the speedometer and the sending unit to allow easy access for making the connection. If your car is one of these, we'll let you know when shipping your 700. We can supply the cable at a small cost.

The sending unit can also be run from an un-driven wheel cable or from an auxiliary cable connected thru a 1:1 tee gear to the odometer cable. A few cars require this setup as it is impossible to mount the sending unit behind the speedometer. In either of these two cases, static electricity may develop in the cable and cause false inputs to the 700. GROUND THE SENDING UNIT BY RUNNING A WIRE BETWEEN THE CAR'S CHASSIS AND THE UNIT. Doing this is very important! Nearly every report of trouble made to Zeronics has been caused by failing to perform this one simple step.

When driving the sending unit from a separate cable, do not over grease the cable. The inner cable core needs only a light coating for proper operation. If the cable is packed with grease, the excess may work its way into the sending unit and block the sensor. The same holds true for a new odometer cable should you replace the one in your car. Don't grease It! The factory sends it ready for use.

The sending unit in not weather proof and any be damaged if left exposed. Always mount it in the car's passenger compartment or trunk. When the sending unit is not mounted underneath the dash, protect it from direct sunlight. High intensity light may leak in through the mating surfaces and cause the unit to operate incorrectly.

Your sending unit comes equipped with the proper cable fittings for your car. If you change cars, they can be replaced with a different type. With replacement, it may be necessary to adjust the washers located on the sending unit's rotor. The bent washers apply a slight drag to the rotor and prevent false outputs from extraneous vibrations. Increase or decrease the drag by bending the washer(s) until the rotor offers a small resistance when turned. Check the drag every 20,000 miles. A diagram of the sending unit's parts and assembly is found at the end of this manual.

Most cars use odometer cables which terminate with a 0.106" square pin. Some British and French cars use a 0.118" pin. Your sending unit comes equipped with the proper rotor to accept the pin size of your car. Should you switch cars, the other size rotor can be ordered from the price list at the end of the manual.

Electrical Connections: A prewired power cord is included with your 700. Connect the red wire to +12 volts (un-interrupted by the ignition switch) and the black wire to ground. Attach the leads as securely as you can make them. Only a momentary power loss, either +12 volts or ground, will erase the data in the 700's displays. Do not select a power 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-on terminals in the holder, strip back the power lead's insulation and attach the red lead at that point. Solder and then wrap with electrical tape for a secure joint. Attach the ground lead under a screw found in a metal part of the car's chassis. Scrape away any paint which might cause a poor electrical path. Using a cigarette lighter plug for your power connections in inviting disaster during a rally.

You will have noted that the power connector has 4 pins instead of only two. The pins are wired in pairs, two for +12 volts and two for ground. If your installation requires additional connectors, follow this system of doubling up on the pins. This is another precaution against a momentary power loss.

A 3 or 4 amp fuse is located in the +12 volt lead of the power cord. Never run your 700 without this fuse in place. It is your protection against shorting the heatsink. A spare fuse to taped to the back of the case. In the unlikely event more fuses are needed, they can be found at most service stations, electronic supply stores and TV repair shops. In desperate circumstances, a fuse from your car's electrical system 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 700 and see if it will turn on. If the leads have been reversed, the unit won't operate. No harm will occur if they have been accidentally switched. This test should be performed without the sending unit connected. Plugging the sending unit in when the leads are reversed may blow out an internal fuse and cause the sending unit to become inoperable.

Keep the sending unit and power connector pins free of dirt and grime. Never wrap masking tape around the pins. A light brushing with steelwool once a year will keep the contact in good condition. You way use tape to hold the connectors together if you feel they might separate because of their location in the car.

Your 700 will operate on voltages from 7 to 20. Fall below 7 volts and data will start dropping out of the displays. Your car's output voltage normally varies between 10 when starting and 14 when charging. A good battery is your best protection against having the voltage go below 7 volts.

While the car's nominal output voltage is 12-14 volts, electrical noise and large voltage spikes can occur at the same time. The 700 has adequate safeguards to isolate it from this type of noise (from fans, lights, etc.). The one exception is solid metal ignition wires. While few cars come equipped with these wires as standard equipment (Alfa Romeos ore one), if your car has them, they need replacement with standard carbon resistance wire. Don't forget the wire between the coil and the distributor.

Porsches have solid wires but are also equipped with suppressors to eliminate the generated noise. No new wires are required. If you feel that solid wires are absolutely necessary, use a shielded type. This wire is available at some automotive parts outlets. It's relatively expensive, but it keeps the noise down.

Don't be tempted to "see what happens" before being convinced to change the wires. In some cases the effect is obvious and immediate ... the counters start rapid and sporadic counting as soon as the car is started. In other cases, hours of close observation may indicate that all is well. Don't be misled by this apparent lack of trouble. This noise can be extremely elusive. Why risk getting bad checkpoint scores. Change the wires!

A small gooseneck lamp to light the 700 during night rallies can be ordered from the price list found at the end of the manual. Two tapped mounting holes are located at the top of the front panel and a power jack is provided on the rear of the case. The lamp comes with a prewired plug, spare bulb, and ON/OFF switch. Do not use the jack or front panel for any other type of electrical connection. Doing so may overload the unit and cause a component failure.


Displays: When the 700 is turned on, the displays will show a meaningless pattern of digits and, in some cases, no digit at all. This random pattern will also warn you that the unit has lost power. If it occurs during your shakedown drives, a faulty power connection must be found and eliminated.

The Odometer records official rally mileage from 00.00 to 99.99 in increments of 0.01 mile. Once you have corrected the 700 at the end of the odometer calibration leg, the mileage in this counter will match the rally's mileage.

The middle display is an Auxiliary mileage register which records distance in a manner similar to the Odometer. It can be used for speed change to speed change mileages on TSD rallies, or instruction interval mileages on stage events.

Real-time-of-day is shown in the Clock display. It counts to 59.99 minutes then returns to 00.00 to start the next hour.

The displays' intensity is controlled by the switch at the bottom of the front panel. Use the BRT (bright) for daytime, the DIM for nighttime. The center position turns the displays off.

Correction Factor: The correction factor adjusts the 700 so it will run at official rally mileage. The four digit factor is set in the thumbwheel switches found at the lower right of the front panel. The formula to adjust your factor at the end of the odometer calibration leg is:

                                          ODOMETER MILES
                             NEW FACTOR = -------------- X OLD FACTOR
                                          OFFICIAL MILES
EXAMPLE: Your factor at the start of the odometer leg is 4500. The leg is 13.71 official miles long and your Odometer reads 13.59 miles at the end.
                                 ----- X 4500 = 4461 (new factor)
4461 is the factor for the remainder of the rally. Of course, you may adjust the factor should later conditions require you to do so.

Before running your first rally, you may want to establish a "base correction factor" (BCF). This is the factor which will run the 700 at statute miles (km) in your car. Once obtained, make a habit of starting each rally with this factor. It will normally keep you within a few percent of the rally's mileage and thus make the odometer leg easier to run.

To find your BCF, it will be necessary to run your car against a known statute distance. Many highways have mileage markers, or you could use an old rally measured in statute miles. When a suitable course is not available, lay one out using the car's odometer. A more precise BCF can be developed when the opportunity arises.

The course for finding your BCF can be any length although it's a good idea to make it at least 5 miles long. Set in a factor and run the course. Use the formula to calculate your BCF. A rerun of the distance using the new factor will find your Odometer's reading equal to the course's "official" length.

There may be times when you will went to adjust your factor during a rally (it may begin raining, etc.). Small changes can be mentally calculated quite easily. For each 0.01 mile you wish to alter your mileage in 10 miles, change the factor by the value of its first digit. Increase the factor to decrease your mileage and vice versa. Suppose your factor is 6012 and you want to increase your mileage 0.01 mile for every 10 miles. Change the factor to 6006 (6012-6). As another example, your factor is 4850 and you need a decrease of 0.02 miles per 10 miles. Change the factor to 4860 (4850 + 4.8 + 4.8).

If you know the number of cable revolutions at the input to the sending unit, you can calculate a BCF from the formula below. A little math will show that a maximum of 1953 revolutions per mile can be accepted by the 700. Most cars have odometer cables running at between 800 and 1200 revolutions per mile. None go over 1600. Direct drives from an un-driven wheel vary between 700 and 1000 depending on wheel size.

CORRECTION FACTOR = Revolutions per mile X 5.12

Most American cars and many foreign models have odometer cables which turn at 1000 revolutions per mile. The BCF in these cases would all be around 5120.

Your 700 will also run in kilometers. Your kilometer BCF would be about 0.62 of your mile BCF (1.00 kilometer = 0.62 mile). The 700 doesn't know what the unit of measurement is, that's for you to decide.

Checkpoint Switch: This control locks the data displayed in the Odometer, Auxiliary and Clock whenever it is thrown to "checkpoint". The counters continue to accumulate information, but this new data is not displayed until the switch is turned off. This feature allows the navigator to hold information he wishes to record. At the same time, the 700 will keep on with its normal operation.

This switch should also be used as you cross a checkpoint's timing line. The mileage to the line (Odometer) and your actual arrival time (Clock) will then be locked In the displays. If you are mis-timed, the Clock will verify the time-in you want. After you are satisfied with your time, turn the switch off. The displays will immediately update to the counter's present data.

Odometer Control Switch: This switch is located just to the right of the odometer display. When it is turned to PWR OFF (Power Off), the power to the 700 and the sending unit is off. In all other positions, the unit is powered.

FWD/OFF/REV (Forward/Off/Reverse) - These three positions control the count direction of the Odometer. Whenever you are switched to +D, -D, or Zero, the Odometer continues to receive and register mileage as if you were still in FWD. The blank positions between PARK and PWR OFF, ZERO and TEST, and TEST and PWR OFF are also FWD as far as the Odometer is concerned. These unmarked positions will prevent you from accidentally switching the 700 into PWR OFF or TEST.

ZERO - To zero the Odometer, turn the switch to ZERO and push the .01 button on the right of the front panel. As mentioned above, the Odometer continues to register mileage when in the ZERO position. It's only when you press the pushbutton that the counter zeroes. Since zeroing requires that you perform both actions, it's unlikely that you will accidentally clear the Odometer during an event.

+D/-D - These positions allow you to adjust the mileage in the Odometer. In +D, the pushbuttons add mileage in increments of 1.00 mile, 0.10 mile and 0.01 mile. -D allows the subtraction of mileage in the same amounts. It makes no difference whether the car is moving or stopped when using these modes. Remember that the Odometer continues to register "on the road" mileage as if it were in the FWD position.

You will use these two positions to set your Odometer to official rally miles at the end of the odometer calibration leg, to adjust for wheel slippage, and to correct the Odometer at checkpoints where your mileage is in error. When returning from an off-course excursion, you will be in REV and unable to use +D or -D. If your mileage should need adjustment, it's not likely to be more than a hundredth or two. Simply wait until you regain the rally course and then make the correction.

PARK - This position prevents the recording of mileage in either the Odometer or Auxiliary. You can switch to PARK to go off course during a break or whenever you do not want mileage registered. You could also accomplish this by turning both rotary switches to their OFF positions. The PARK mode, however, has one important additional feature. Whenever the 700 is taken out of PARK, the next distance pulse will not register until you have traveled 0.01 mile (km). The 700 continuously calculates distance and may generate a distance pulse shortly after the Odometer or Auxiliary is turned on. If this happens at the beginning of the odometer calibration leg, your mileage will be slightly in error. You can assure an accurate measurement by pulling up to the Start line in PARK, or by momentarily switching to it while you are there. This feature of PARK is also useful at the end of the Odometer calibration leg, at the end of transit zones and whenever the rally's mileage is zeroed.

At a checkpoint out-marker, the Odometer may have pulsed 50 feet prior to it. The next count would now occur shortly past it. Your time calculations for the next leg would be based on about 0.01 mile too great a distance. A quick switch to PARK will make the first count occur 0.01 mile after the leg begins.

TEST - This position activates an internal pulse generator which causes the 700 to run as if it were in a moving car. You can test or demonstrate the unit in this mode. The 700 behaves like the car is going 60 mph (kph), 1 mile per minute, when the correction factor is 4096.

Auxiliary Control Switch: This control selects the mode of operation for the Auxiliary and is also used to set the Clock. The OFF, REV, +D, -D and Zero positions operate as described in the Odometer section, M1 (Mode 1) is the same as FWD. The Auxiliary is in M1 when you are switched to a blank position or in any of the Clock positions.

M2 (Mode 2) - This position, when used with the Checkpoint switch, lets the Auxiliary serve as a point to point mileage register. When the Checkpoint switch is thrown, the Auxiliary's information is held as previously explained. Once the information is locked in the displays, the counter zeros and begins accumulating distance from the point where the switch was thrown. When the switch is turned off, the Auxiliary shows this new mileage and continues to count normally.

Most unequipped calculation methods use speed change to speed change mileages. Mode 2 lets the navigator write this mileage down while the Auxiliary begins measuring the distance traveled at the new speed. On stage events with instruction interval mileages, a quick switch into and out of Checkpoint will zero the Auxiliary for the next mileage.

An external jack is located on the back of the case for use in zeroing (not splitting) the Auxiliary when it is in Mode 2. If you run stage events, you may find it more convenient to have a separately mounted zeroing switch. Simply wire the plug provided with your 700 so that the circuit is completed when you activate your switch. See the diagram at the end of the manual.

Setting the Clock: The Clock is set by using the three Clock positions on the rotary switch and the pushbuttons. The Auxiliary continues to run in Mode 1 while you are in any of the setting positions. To zero the Clock, switch to ZERO and press the .01 button. To stop the Clock, switch to HOLD and press the .01 button. 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 as follows. Just prior to an even minute on your time reference, zero the clock. While still pressing the .01 button, switch to HOLD. The Clock will now be held at 00.00. When the even minute arrives, release the button. The first time count will occur exactly 0.01 minute later. This has set the hundredths part of the Clock. 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.


The accuracy of your 700 is much greater than you will need on a rally. When your correction factor falls in the normal 3000 to 6000 range, you can correct your mileage to about plus or minus 0.01 mile in 60 miles. If you and the rallymaster can agree to within 0.01 mile after 10 miles or so, that would be about normal with all things considered.

The Clock will stay within 0.01 minute over the period of an all day event. Extreme temperature fluctuations may slightly affect its accuracy. This may happen should you leave the 700 turned on overnight in cold weather. Even in these cases, the Clock will not vary by more than 0.02 minute per day.

The 700 has been constructed to withstand all the normal jolts and bounces it might receive during a rally. When using your 700 on stage events, don't mount the unit rigidly to the car's frame. This will only transfer every shock taken by the car directly to the 700. Application of a little care in your mounting arrangement will insure many years of trouble-free rallying.

Although your 700 is built only with quality components, there is always the possibility it may stop functioning correctly. As a first step in correcting the problem, notify Zeronics and describe the malfunction. It may not be necessary to return the unit. Most major parts are mounted in sockets for easy removal and replacement. The feature is found on all Zeron models. It's your assurance of quick and inexpensive repair of any problem you might have.


Install the 700 and check that it is properly connected and in good working order prior to leaving for the rally. As with all rally equipment, the 700 is useless when part of it is home in the closet and you are at the start.

Turn the 700 on about 30 minutes before you time out. Zero the counters and set the Clock to time of day. Enter your BCF (let's call it 4500). Switch to PARK. The remaining time can be spent double checking your equipment and going over the general instructions one final time.

0.00 1. Begin odometer calibration leg at "Start".

Check your Odometer to be sure that it is zeroed, then switch to FWD.

8.69 2. End odometer calibration leg at "Trap". Begin 30 mph.

Write down the mileage in the Odometer (let's call it 8.78), adjust the Odometer to 8.69, switch into, and then out of PARK. Switch on the Auxiliary if you are going to use it, and then pull ahead to clear the area for other cars. Your new factor is not in yet, but a short distance at the old one won't give you any discernible error.

Calculate and enter your new factor (4547).

CHECKPOINT! Throw the Checkpoint switch as you cross the timing line. Compare the Clock with the time given you by the workers. If there is a discrepancy, straighten it out before turning the switch off. When you are satisfied with your time and have recorded whatever information you need, switch out of Checkpoint and pull ahead to the out-marker. Adjust your mileage if necessary, then clear the marker to wait for your time out.


(Subject to change without notice):

The following items are available should you change rally cars or set up a second car. We pay the shipping charges.

    Sending unit (specify car make and year or type of fittings)  $45.00
    Rotor (specify for 0.106 or 0.118 shaft)                        8.50
    Night light                                                    10.00
    Power cord (prewired with fuse and holder)                      5.00
    Halda T-Gear (used for new sending unit fittings)              20.00
For a fee of $7.00, you may return your sending unit and have the fittings exchanged for a different type. This offer is good only when the fittings to be switched are still being used on a currently produced car. Your old fittings will be kept by Zeronics and the new ones will be mounted on your sending unit. The rotor drag will be adjusted and the unit will be inspected.


Zeronics Engineering warrants all of its products to be free from defects in workmanship and material for a period of one year from original purchase. Our obligation under this warranty is limited solely to repairing 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 purchaser, (2) no modification or change has been made to the unit's circuitry or wiring, (3) the unit has not been damaged by misuse, neglect, improper operation, accident, or alteration as determined by Zeronics Engineering. No other obligation is implied or expressed.

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