Using a 106 series SCR, this circuit was found in the May 1971 Radio Electronics magazine. The quiescent current is very low and is given by the value of R1.
The oscillator in figure 1 can be used in alarm, call or warning systems, producing a sound of...
This circuit is from a 1973 documentation. In it we have the way of using a FET as an input of...
This circuit is for traditional old-style telephone lines found in an American 1980s...