This circuit generates a siren sound. It was found in the April 1969 Radio Electronics magazine. The output signal is to be applied to an external amplifier.
Found in a 90’s HAM Radio, this circuit is used for an optical communications system or even audio...
This circuit is from a 60's documentation. The capacitance C1 can be between 20 pF and 0.01 uF...
This circuit is from an old French documentation from the 70s. The coupler admits equivalents and...