This circuit for monitoring telegraphy transmissions was found in a 1975 CQ magazine. Transistors may be modern equivalents.
This VCO makes use of components from the 1980s. The circuit can be implemented with modern...
The amplifier shown shown is based on the MAX9715 integrated circuit from Maxim (www.maxim-ic.com) providing an...
This old configuration, using a unijunction transistor (UJT) controls a LED than blinks if an...