This circuit activates an old cassette recorder when the phone is being used, thus making it possible to record the conversation. The circuit is from a Hands On Electronics from the 90s.
Found in a 90s 73 magazine, this circuit uses an unusual component today which is the XR2206. |...
This random noise or white noise generator was published in Radio Electronics magazine in July...
This circuit was found in Philips documentation from 1967. The phototransistor is from that time,...