This circuit was found in the Electronics Experimenter Handbook from 1991. The circuit controls a simple relay for the purpose of turning circuits on or off or switching audio channels.
This circuit of a 1978 American publication monitors a telephone line by triggering a relay. The...
Found in 1965 General Electric technical documentation, this half-wave circuit controls shunt type...
The power supply shown in the figure provides voltages between 0 and approximately 15 volts, with...