This circuit was found in the March 1980 issue of Radio Electronics magazine. It is based on the newly released LH2400. The circuit must be powered by a symmetrical power supply.
In critical applications of the RS-232 interface, the danger of induced voltages in the cables must...
When S1 is pressed, the circuit allows music to be played from an audio source on the telephone line....
We found this circuit in an American publication from the 1980s. Equivalent modern operational amplifiers...