The circuit is of the Motorola Linear Databook of 1990. The power source must be symmetrical and the characteristics of the circuit are given next to the diagram.
The values of the capacitance between output A and ground can be programmed digitally in 18 steps...
This circuit is the traditional 555 oscillator that produces a hum in the piezoelectric...
This circuit activates an output, which can be a lock, only when a card containing the programmed code...