This circuit makes use of an optical coupler to isolate the telephone line. The circuit is from 1970s documentation. The components admit equivalents.
We found this project in a 1982 publication. What we have here is an audio signal relay trigger, which...
This power supply was originally designed to power the amplifier shown in CB16743E, but it can be...
This circuit generates signals for adjustments in FIs of 10.7 MHz. The transistors can be BC548 or...