We found this circuit in a 1991 Hobbyst Electronics. The circuit makes use of an unusual transducer today. It is a piezoelectric buzzer that can eventually be replaced by an equivalent configuration.
May 2017 - These new Digital to Analog converters from Texas Instruments, available from Mouser...
This simple alarm with SCR triggers a buzzer. It was found in the Encyclopedia of Electronic...
Found in American documentation, this circuit converts signals from the 27 MHz band for reception on an...