Using junction FETs, a configurable configuration is achieved for very low frequencies. FETs can be of almost any type and the frequency depends on the capacitors.
This simple metal detector was found in a 1960 Sylvania transistor manual. The phone must be high...
The figure shows how to obtain an 800 Hz astable circuit controlled by an external signal. The...
We find this circuit in an American 1980s documentation. It can be applied to any operational...