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 circuit was found in the September 1974 issue of Radio Electronics magazine. The circuit uses...
This circuit was found in the December 1983 issue of Radio Electronics magazine. The sensor is an...
We found this circuit in a 1975 publication. The circuit can be made with more modern equivalent...