This circuit for audio signals was found in the March 1990 Radio Electronics magazine. The circuit uses a unusual optocoupler that can be replaced with an equivalent one.
This simple intermittent siren circuit was found in a 1989 documentation. Both the intermittent and...
This 1967 Electronics World circuit is suitable for frequencies up to 1 MHz. The setting applies...
This circuit was suggested by Sprague Electric in an 80's documentation. The circuit uses a...