Found in an Elektor from the 90s, this circuit converts signals from the 280 kHz band to 516 kHz, making it possible to tune them in common AM radios. The components used are from that time.
This contact or reed switch actuation was found in a 1964 Electronic Design. The circuit can be...
This circuit was obtained from a 1985 Electronic Desing. The circuit uses a Darlington which may be...
This configuration that appears several times with variations on this site is from old American...