A push button connected to input E0.0 activates a series of light bulbs connected to output A2.1 for a period of three minutes. Together with the lights, a pilot light is also connected to output A2.2. This light will begin to flash 15 seconds before the lights go out to indicate that the time is almost up. This pilot light goes out at the same time as the lights.

Timers T2 and T3 are used to generate a square wave with a period of 1 sec. and a working cycle of 50%. Both are loaded with a time constant of 50 hundredths of a second. See Example 21.
Two additional extended pulse timers are also used. T1, loaded with a time of 3 minutes (KT180.2 that is 180 seconds), directly controls the output to the series of lights. T0, loaded with a time of 15 seconds less (KT165.2) is used to determine the time when the pilot light should begin flashing.

Diagram of the timer control for lights

The development in time of T0 and T1 after the pulse on E0.0 are shown in the second and third lines of the above diagram. The fourth line shown on the trace, not to scale, is the timer T2.
In the fifth line of the diagram it is possible to see that the pilot light should be lit either when T0.0 is active or when A2.1 and T2 are active at the same time that T0 is inactive. In boolean terms this is:
A2.2 = T0 OR (A2.1 AND NOT T0 AND T2)
The proposed solutions implement the description with extreme precision.
The first, construed in ladder format, uses the first two paths to construe the signal of the square wave. The next two activate the timers for the lights and the pilot light.
The first group of statements in the AWL program generates the signal for the square wave. The second group starts the timers for the lights and the pilot light. The third group turns on the lights and the fourth and final group lights the pilot light as indicated by the expression above.

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