This circuit was found in a 90s Popular Electronics. It is used for the acoustic transmitters of 40 kHz, as several found in this section. Transistors support current equivalents.
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...