This type of answering machine was common at the time this circuit was published. Using two tape recorders, it was published in the June 1986 issue of Radio Electronics magazine.
This microphone preamp found in a 1995 documentation offers stable microphone operation. The...
This high input impedance amplifier stage was found in a 1963 documentation. The transistor...
We found this oscillator in an English documentation from 1977. The symmetrical supply, in fact,...