This circuit was obtained from a National Semiconductor manual from the 1990s. The circuit employs a pair of matched transistors, and the indicator is analog.
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...