This circuit is recommended for alarm systems since it has a good output stage. The circuit is from a Radio Electronics magazine from October 1992.
This circuit matches a source of high or medium impedance audio signals with a low impedance...
Found in a 1993 Electronics Hobbyst Handbook, this circuit uses components that are still common...
This pulse width-tuned circuit was found in the March 1996 issue of Electronics Now magazine. The...