Found in the CQ radio amateur magazine, this circuit generates a standard 100 kHz signal. The circuit is from 1965 and can be made with modern equivalent transistors.
The frequency of this astable depends on the capacitor that can be changed over a wide range of...
This circuit is from a documentation from the 90s. The transistor can be any general-purpose FET...
In the figure we have one of the many options found in this section for an intercom using ordinary...