Found in American documentation from the 1980s, this circuit has a throughput of 700 Hz and a flat response of 400 to 500 Hz, with crystals of 3 MHz. Crystals of 2 to 15 MHz can be used.
This Rytron transmitter was published in a 1953 book. The circuit can be implemented with a BC558...
Foto-Darlington for applications such as light sensor. In normal applications only the collector and...
This circuit was found in a 90s Popular Electronics. It generates tones given by the oscillators and...