This circuit was found in a 1967 Electronics World. Transistor Q1 can be a TIP321 and Q2 can be a BC558. The indicator lamp is optional.
Used with telephones at the time, this circuit was found in Popular Electronics from the 90s. The...
Unlike the CIR4620 circuit, the circuit shown in the figure operates by capacitance. This means...
This 1 A circuit was found in a Philips documentation from 1966. The transistor is of the time,...