TRUTH TABLES AND EXERCISES
Identify by number the following logic symbols:
How long must the safety signal be present before the time delay (1) will pass an output
(on) signal to Gate 2?
Under what conditions will Gate 2 turn on?
Under what conditions will the low flow alarm (5) sound?
Since the control switch is always in the AUTO position (due to the spring return
feature), what logic gate keeps the continuous on signal that is generated by the control
switch being in the AUTO position from starting the fan? What signal must also be
present to allow the AUTO signal to start the fan?
If 12 minutes after first receiving a safety signal, with the fan control switch in the
AUTO position, the safety signal is removed (off), what will happen to the fan? Why?
How many ways can the fan be started? How many ways can the fan be stopped?