By Russ Jensen

The term relay race refers to relay circuitry in which one relay, when energized energizes a second relay, which can then energize a third relay, etc. A relay, when energized, normally would de-energize the relay that energized it. A variation of this idea has been employed in games (mostly older games, before the introduction of the score motor) usually to provide multiple impulses for scoring functions.

(NOTE Genco used this type of circuitry in games up into the 1950s and, as far as I know, that company never used a score motor.)

An example of a circuit employing this idea is shown in Figure 6. While this is a hypothetical and somewhat simplified example, the principles involved in the operation of this circuit are typical of those of this type of circuit. The example shows a circuit to provide multiple scoring (for example, scoring of 5 points by registering 1 point five times).

The circuit involves a "Control Relay" with a hold on circuit that, when energized by the closing of an external switch (labeled Start SW" in the example), will start the circuit in operation and keep it going until it has completed its job. A stepping switch is used to count the number of points scored and disable the circuit (by providing the drop out function for the "Control Relay") when 5 points have been scored. The timing of this circuitry is provided by a relay, (labeled "Impulse Relay") one of its switches energizing the "Score Relay" 5 times to provide the actual scoring. The step-by-step operation of this circuitry will now be described.

When the "Start SW" is closed (by some action in the game that entitles the player to five points) the "Control Relay" is energized. It is held in by its hold on circuit, via the normally closed switches (drop off switches) labeled "OA Last Step" and "OA Beg. of Stroke" (both of which will open when the stepping switch has completed five complete steps). This provides coil power to the line labeled "Controlled Power," which provides power to the other circuitry.

As soon as power is applied to this line the "Step Coil" of the stepping switch is energized via the normally closed switch, ("SW#1) on the "Impulse Relay" and the stepping switch starts to step to its first position. When the "Step Coil' plunger has completed its inward motion, its end-of-stroke switch (labeled "Step SW EOS") is closed thus energizing the "Impulse Relay."

The energizing of the "Impulse Relay" energizes the "Score Relay" by its normally open switch (SW#S) thus scoring one point and opening the circuit to the "Step Coil" by means of the normally closed switch (SW#1), which is in series with the "Step Coil," thus allowing its plunger to return to its normal at rest position. You will note that the "lmpulse Relay” has a hold on circuit utilizing the normally closed (drop out) switch, labeled "OA Beg. of Stroke," on the stepping unit. This switch closes as soon as the "Step Coil” is energized and remains closed until that coil is de-energized and its plunger has fully returned to its at rest position. This hold on circuit thus assures that the "Impulse Relay" remains energized during the time that the "Step Coil” plunger is returning from its end of stroke position to its normal at rest position.

At this point one cycle of this circuitry has been completed (one of the five points has been scored). As soon as the "Impulse Relay" opens (when the "Step Coil" plunger has returned to its at rest position) its normally closed switch will again close, energizing the "Step Coil" once more and the entire process will be repeated, thus scoring the second point. It can easily be seen that this will happen five times (scoring five points), but on the fifth cycle something else will also happen.

When the stepping switch makes its fifth step, the normally closed switch (labeled "OA Last Step"), which is in the hold on circuit for the "Control Relay," will open. This will not yet drop out the "Control Relay" however, due to the normally closed switch (labeled "OA Beg. of Stroke"), which is wired in parallel with this switch. This second switch (often referred to by game designers as a safety switch) will keep the "Control Relay" energized until the stepping switch plunger has fully returned to its at rest position after completing its fifth step. This ensures that the "Impulse Relay" will be held on for the same period as in the previous cycles to guarantee a good impulse to the "Score Relay" coil.

(NOTE: The circuitry shown in this example does not include a method for resetting the stepping switch after the fifth step This would vary depending on the type of stepping switch used. If a reset type were used additional circuitry would be required to energize its reset coil after the fifth step. If a continuous type was used the "OA Last Step" switch could either be implemented using contacts on the stepping switch disc or a cam could be attached to the rotatable shaft of the stepping switch with a notch at every fifth position to actuate the "OA Last Step" switch.)

It should be noted that in this type of circuitry, adjustment and proper operation of most of the switches is extremely critical. One malfunction or misadjusted switch can cause erratic operation of the entire circuit, and if more than one is bad. Watch Out! For example, the adjustment of the "Step SW EOS" and "OA Beg. of Stroke" switches control the timing of the entire circuit; the former determines when the "Impulse Relay" will be energized and the latter determines when it will drop out.

This concludes the discussion of typical circuit configurations used in games Although this discussion was by no means exhaustive, some of the most commonly encountered, difficult to understand, and important circuits have been discussed. The important thing, as far as troubleshooting is concerned, however, is the understanding of the principles involved. To tie up the discussion of game circuits an example of a complex game function will now be discussed.


Since we have now examined all the basic game components and many of the basic and typical game circuits, we are ready to examine an example of a complex circuit in which several circuits acting together produce a game function. In this case, the multiple scoring of points You may notice that this is a similar function to that used to illustrate the relay race, but this repetition serves several purposes. The present example shows everything associated with this function including the control of the score indicating lights. In addition, it illustrates the uses of the "Score Motor" while providing an example of the timing function application of the relay hold on circuit (as well as the assurance, or feedback, function). In short, this example will tend to tie together most of what has been covered by the previous articles in this series.

(NOTE: The circuitry in this example will also be used in connection with the discussion of trouble-shooting techniques to be presented in the final part of this series)

Figure 7 illustrates the basic circuitry required to score 50,000 points (in increments of 10,000 points) such as would be found in a typical 1950s pingame. Basically, the ball in play would strike a bumper or target whose value was 50,000. This would initiate the action of the circuitry and cause the “10,000 Step-up Unit" to advance five times, displaying the changing score (in units of 10,000) on lighted panels on the backglass. The step-by-step operation of this circuitry will now be described.

First, note the switch labeled "50,000 Bumpers" to the lower right of the "50,000 Relay" coil When a ball strikes one of these bumpers this switch (actually it may be several switches wired in parallel) would close, thus energizing the "50,000 Relay" coil. Once energized, this relay is held in by its hold on circuit via its normally closed drop out switch labeled "Motor 5A."

(NOTE: This relay and its hold on circuit is a good example of the timing function of hold on circuits previously referred to. This will become more apparent as this discussion progresses.)

The energizing of the 5O,OOO Relay" closes the switch by the same name, which supplies power to the "Score Motor," starting the motor unit rotating At the beginning of the motor cycle, the switch labeled "Motor Run" will be closed by one of the "Score Motor" cams. Since this switch is in parallel with the "50,000 Relay" switch, the motor will continue to rotate until the end of the motor cycle after the "50,000 Relay" is de-energized.

(NOTE: You will notice the notation "Other Motor Start Switches" to the right of the "50,000 Relay" switch that starts the motor. This is to indicate that in all games there are many switches in parallel with the "Motor Run" switch, each of which will start the "Score Motor" for one of the game functions requiring motor action, such as game resetting, multiple scoring, kickout hole operation, or any other operation requiring events to occur in a timed sequence.)

As you will recall from the discussion of "Score Motors" in Part 4 of this series all "Score Motor' units have 'Impulse Switches," which normally close and reopen five times for each motor cycle. One of these switches, labeled "Motor Impulse" can be seen in Figure 7 to be connected in series with a switch labeled "50,000 Relay" and supplying power to the "10,000 Relay" coil. Since the "50,000 Relay" is held on (and hence its switches are closed), as soon as the "Motor Impulse" switch closes the first time, the "10,000 Relay" will be energized. You will notice that that relay has a hold on circuit utilizing a normally closed switch labeled "10,000 Step Up E.O.S." This circuit provides an assurance function to assure that the "10,000 Step Up Unit" steps before the "10,000 Relay" is allowed to drop out. This hold on function also is necessary to keep the relay energized after the "Motor Impulse" switch reopens.

(NOTE: You will note the switch labeled "10,000 Contacts" also capable of energizing the "10,000 Relay." This represents any other circuits in the game that can score 10,000 points such as rebound rubbers, "10,000 Bumpers," etc. While this switch symbol actually represents several switches wired in parallel, schematics will often illustrate these as one switch, appropriately labeled, to save space on the drawing.)

The energizing of the "10,000 Relay" energizes the "10,000 Step Up" coil on the "10,000 Stepping Switch" via the switch labeled “10,000 Relay." The stepping switch will thus advance one step. One of its wipers would then make contact with the disc contact wired to the 10,000 score lamp (shown as the number "10" enclosed in a circle In the figure) thus supplying lamp power to light that lamp behind the backglass. During this operation (when the plunger of the "10,000 Step Up" coil has been completely pulled in) the ”10,000 Step Up EQSL" (end of stroke) switch opens thus dropping out the "10,000 Relay." This feedback provides the assurance function mentioned earlier.

During all this time (actually only barely a second) the "Score Motor" is rotating and shortly after the scoring sequence just described is complete, the "Motor Impulse" switch will close for the second time The 10,000 Relay" will again be energized and 10,000 more points will be scored. This sequence will occur a total of five times (once for each closing of the "Motor Impulse" switch) thus scoring 50,000 points. At that point the stepping switch wipers will have reached the disc contact connected to the 50,000 lamp behind the backglass, thus illuminating it.

(NOTE: If the "10,000 Step Up Unit" had been at some score other than zero at the start of the sequence (say 20,000) then it would be 50,000 higher (70.000 in that case) when the scoring sequence is completed).

Almost immediately after the "Motor Impulse" switch reopens for the fifth time the motor switch labeled “Motor 5A" will open. You will recall that this switch is used as the drop out switch for the "50,000 Relay" and has been holding that relay energized since the start of the sequence of operations being described. When the switch opens, the "50,000 Relay" will immediately drop out (become de-energized), thus opening its switch, which was used to allow motor impulses to energize the "10,000 Relay." Remember, however, that the "10,000 Relay's" hold on circuit will keep that relay energized until the last 10,000 points have been scored.

Shortly after the "Motor 5A" switch opens the "Motor Run" switch will open and the "Motor 5A" switch will again close. You will note that since the "50,000 Relay" is no longer energized, the motor will stop (when the "Motor Run" switch opens) and the "50,000 Relay" will not be energized by the closing of the "Motor 5A" switch since its hold on switch ("50,000 Relay Switch") is now also open. This completes the operation of the 50,000 scoring sequence. A subsequent closing of one of the "50.000 Bumpers" switches would, of course, start the whole sequence again scoring an additional 50,000 points.

The sequence just described includes a good exam pie of the timing function of a relay hold on circuit in the operation of the "50,000 Relay." This relay was energized at the start of a motor cycle (before the first impulse) and was held on until the end of the cycle (after the fifth impulse) allowing all five impulses to reach the "10,000 Relay." Had this relay been dropped out earlier (say after the third impulse, for example) a fewer number of impulses (three in this case) would have been allowed to energize the "10,000 Relay" thus scoring fewer (30,000 in this case) points. This type of circuitry is abundant in games where scoring of some multiple number of points (or other situations requiring multiple impulses) is desired.

We have, at this point, concluded the discussion of game components and typical circuitry.

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