## Timing Circuit's Timing Diagram

The timing diagram above corresponds to the circuit above. Lights A, B, C, D, and E come on, in order, as before. However, the behaviors of lights F, G, H, and I are more complex.

When light B comes on at time 1, relay J closes. Then electricity can go from the top of the battery (a triangle in the circuit diagram above), through closed relay J and normally closed relay K, to light F. Therefore, when light B comes on, light F also comes on. However, when light D comes on at time 3, normally closed relay K opens and light F goes out. That is, at time 1, F comes on and, at time 3, F goes out as indicated in the timing diagram.

Similarly, light G comes on when light B comes on, and light G goes out when light C comes on. Similarly, light H turns on when light D comes on, and light H goes off when light E comes on.

The behavior of light I is more complex. At time 1, light B comes on and relay P closes. Electricity can then go through keys P and Q to light I. At time 2, light C turns on and normally closed relay Q opens, turning light I off. Therefore, light I turns on at time 1, and goes off at time 2. At time 3, light D comes on, relay R closes, and electricity goes from the top of the battery, through key R and the normally closed S key, to light I. At time 4, light E turns on and normally closed relay S opens and light I goes off. Therefore, light I turns on at time 1, off at time 2, on at time 3, and off at time 4.

## With Processor Power (PP) Loop

The circuit above is the same as the previous circuit except that all but one connection to power is replaced by a connection to loop 'PP.' ('PP' stands for Processor Power.) After key 'PP' is pressed, key PP stays down and power goes to the circuit. Then, when key J is pressed and held down, output signals F, G, H, and I are generated as indicated in the timing diagram, above. Notice how the right-hand side of the circuit above looks somewhat like the right-hand part of the timing diagram above.

## With Feedback Through Normally Closed Key K

In the circuit above, key J in the upper left has been replaced by the normally closed relay K in the lower center of the circuit. The circuit above generates the timing diagram below when loop key PP in the lower left is pressed at time 0. Loop PP stays down after it is pressed.

When PP is first pressed, electricity can flow from PP, through normally closed relay K to light A and to the electromagnet of relay L in the upper left of the diagram. Relay L then powers relay M. As the relays turn on, one after another, lights B, C, D, and then E turn on. When light E turns on, the normally closed relay K opens, light A goes out, and relay L opens. One hundredth of a second after relay L opens, relay M opens because electricity is no longer getting to the electromagnet of relay M. The relays in the delay line then open one after another and lights B, C, D, and E go off one after another. When light E goes off, no power gets to the electromagnet of normally closed relay K and relay K closes. When relay K closes, electricity can get to light A and then lights B, C, D, and E turn on.

Thus, A, B, C, D, and E turn on one after another. Then A, B, C, D, and E go off one after another. Then A, B, C, D, and E turn on one after another. Then A, B, C, D, and E go off one after another. This pattern repeats as long as loop key PP stays down.

Light F is on only when light B is on and light D is off. Similarly, light G is on only when light B is on and light C is off. Also similarly, light H is on only when light D is on and light E is off.

When light B is on and light C is off, relays N and O are closed and light I is on. Similarly, when light D is on and light E is off, relays P and Q are closed and light I is on. Therefore, light I is only on when light B is on and light C is off and when light D is on and light E is off.

The circuit above is called a clock. It generates signals F, G, H, and I over and over again as indicated in the timing diagram below.

## Timing Diagram with Feedback

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