This circuit is from the 80's but uses common components today. The relay is voltage sensitive according to the power supply used. Transistors may be general purpose types.
We found this circuit in the National Semiconductor Audio Handbook of 1977. The circuit produces...
We found this circuit in an old publication dealing with operational amplifiers. The circuit uses...
I found this circuit on a December 1976 Radio Elettronica. The Italian magazine no longer exists, but...