This 4-transistor timer was found in the April 1975 issue of Radio Electronics magazine. It uses both single-ended and single-junction transistors to provide a dual audio output.
This circuit was obtained from an American documentation from the 1980s. The T1 triggering...
Found in a 1974 Ferranti manual, this circuit uses diodes to limit the voltage on the transistors. The...
This circuit is from an English publication of 1991. With it you can use a common multimeter on...