Based on the Philips TDA3810N, this circuit was found in an 90s Electronics Now. The circuit has two channels including the voltage regulator stage.
The sound produced by this circuit, from a 1978 publication, depends on the humidity between the...
In a September 1992 Radio Electronics article, we found this basic 555 circuit used to generate fixed...
This circuit is suggested by Motorola, using a 4N26 type coupler and an MC1733 type operational....