We found this circuit in the November 1984 Radio Electronics magazine. The base frequency is given by C1. The power supply can be between 3 and 12 V.
This very old circuit, from a publication from the 1970s, uses a germanium transistor and two...
In the figure we have a very sensitive touch switch circuit. A touch of the sensor causes the...
In fact, we can say that this circuit found in documentation from the 90s, consists of an intercom...