In the figure we have the way to control a flip-flop with the 4069 from positive pulses. The circuit can be used as a shield, if powered by 5 V.
This interesting transistor circuit has several effects and an included amplifier. The circuit is...
Found in Elektor Electronics from the 90s, this circuit produces the tone of 1 750 Hz for calling VHF...
This simple 2-transistor radio is from Radio Electronics in October 1952. The circuit outputs a...