This circuit was obtained from HAM Radio magazine in an 80's issue. The FETs are types of the time and the frequency is determined by the crystal. The circuit operates at voltages from 3 to 9 V.
This didactic circuit was found in a 2001 documentation. It automatically counts in an increasing and...
The presence of a pulse at the CTRL input produces an audio signal of duration determined by the...
We found this circuit in an old documentation, using an operational of the time. The circuit...