Found in an American 1980s documentation, this circuit compares signals from two TTL sources, providing an output that depends on the frequency difference. The circuit can be used as a shield.
This circuit was obtained in a publication for radio amateurs of the 70s. The PNP output...
This circuit uses na Unijunction Transistor (UJT) to produce a modulation tone for several...
This circuit was originally found in a Philips documentation from 1969. It is intended for sensing...