This simple unijunction and bipolar generator appeared in Radio Electronics magazine in September 1865. It generates signals from 100 kHz to 60 MHz and is powered by two 9 V batteries.
The circuit in the figure is based on an LM101A; diodes can be replaced with equivalents. The...
This circuit, with magnetic sensor, uses an operational amplifier of the time. The circuit is from...
Found in a 90s Popular Electronics, this circuit checks if a remote-control transmitter is...