Suggested by Philips documentation from 1968, this circuit uses components from the era that can be replaced by modern equivalent types. The double transistor can be replaced by a matched pair.
When S1 is pressed, the circuit allows music to be played from an audio source on the telephone line....
This circuit was found in an Experimenters Handbook of the 1990s. The purpose of this circuit is to...
The action of this circuit, found in a 1977 amateur radio documentation, is like to a delay line....