In the figure we have a good rectangular signals generator with several frequency bands. The circuit is based on old logic but can be implemented with modern equivalents.
This 1969 Philips documentation circuit makes it possible to control an engine through the sound...
The absence of a pulse in the pulse train applied to the input of this circuit causes a high level...
Found in a 1970's Radio Electronics, this circuit uses a triac to switch loads on the AC network. This...