This telephone recording circuit was found in the June 1979 issue of Radio Electronics magazine. The components are common at the time and the power is supplied by the power grid.
This circuit is from old documentation. The operational amplifier is uncommon nowadays. The...
This memory flip-flop must be powered by 5V voltage. The circuit stores 1 bit. ...
This simple preamplifier was published in Radio Electronics magazine in February 1958. The battery...