Found in a Popular Electronics from the 90s, this circuit activates a recorder for automatic recording of telephone calls. The circuit was used with old cassette recorders of the time.
We found this test circuit in a March 1967 Radio Electronics. The circuit uses a zener-regulated supply and...
This amplifier for small cassette tape players was found in an English documentation from 1969. The...
We found this circuit in a 2005 Linear Technology manual. The resistor is calculated for the...