Found in Electronics now from the 90s, this circuit uses a sensor from the time, which is difficult to find today. The circuit activates a sonalert-type buzzer.
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...