This circuit was originally recommended to give the call signal on intercoms. However, it can be used with other applications. The circuit is from 1978 documentation. The transistor may be the BC548.
This three-transistor circuit was found in Radio Electronics magazine from May 1969. The circuit is...
This beat frequency oscillator was found in a 1980s documentation. The original FET has a grounded...
With this circuit it is possible to make the selection of transistors and their test according to the...