Found in a 90’s Popular Electronics, this circuit uses a component that can be difficult to obtain today. It achieves a 10 dB noise reduction with the indicated components.
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...