With the configuration shown in the figure, we have the relay being activated when the microphone picks up a sound and shutdown when the X1 reset sensor is activated.
We find this circuit in an 80's EDN. The circuit can be used with equivalent operational,...
This full-wave circuit was obtained in Motorola's 1974 unijunction transistors manual. The circuit...
This circuit was found in Motorola documentation from 1966. The lamps are according to power and...