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 amplifier was found in a Japanese publication in 1972. Transistors are uncommon today, and...
The current of this source is 200 mA at the most, and the output depends on the zener that may...
Found in Mallory documentation from 1968 this circuit uses an integrated circuit from that time. The...