Found in American documentation, this circuit can make use of modern equivalent transistors. The circuit triggers with positive pulses.
This circuit was taken from the 1960's Mullard Transistor Manual. Information about the coils is...
This bridge circuit is designed for 8-ohm speakers delivering a few watts of power. The circuit is from...
This alarm, from a 1996 magazine, can be fitted with two BC548s in the original configuration...