This circuit was suggested by Motorola in a 1980s publication. It is based on a PUT that is not a common component today. The division depends on the capacitor values according to the table.
This circuit was found in old American documentation. Transistor is general purpose and relay is...
This circuit is from a 1984 magazine, but it can be assembled with a BC558 for TR1, BC548 for TR2...
We found this circuit in a European publication from the 1980s. The circuit uses a low impedance...