This flip-flop circuit with general purpose transistors was found in American documentation from the 1980s. The maximum operating speed depends on the transistors. Diodes are commonly used.
This antenna for the frequencies 146 or 440 MHz was found in a magazine 73 for Amateur Radio of...
This circuit produces 1 kHz square signals using the CMOS IC 4070. The frequency is given by the...
Found in a 90s PE Hobbyst Handbook, this circuit mimics the sound of a space gun. The components...