This circuit can activate a powerful lamp or call system when a telephone call occurs. Suitable for hearing impaired or noisy places it was found in American documentation in the 90s.
This device can be used as a proximity arm, touch sensor or electronic bell. When connected to a...
This circuit is from the component's own manual, but it applies to others in the same family. The...
This circuit was found in a 90s Popular Electronics. The circuit uses several relays in order to...