This circuit is from American documentation from the 70s. The circuit makes use of the operating system of the time, but it can be implemented with more modern equivalents.
This circuit of an old publication makes use of SCRs that admit modern equivalents. The frequency...
This 1977 circuit is a simple and straightforward application of an SCR, already explored in many...
The current drained by this circuit, from a 1976 documentation, is 3 mA and the cut-off frequency is...