Found in Popular Electronics from the 90s, this circuit turns off an appliance at the end of the programmed time. The 12 V relay must have contacts according to the controlled current.
In the figure we have the basic configuration of an operational amplifier for audio signals. The...
This General Electric circuit produces pulses of light only when light stops shining on the...
Found in an Electronic Design of 1964 this circuit has a control for the frequency and another for the...