Found in a 1969 British publication, this circuit uses a regenerative switch with two transistors to produce pulses that depend on C1. The relay must be in accordance with the supply voltage.
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...