This circuit was obtained from an American 1980s documentation. The frequency depends on the crystal and the circuit may be a PNP that reaches the generated frequency.
This is the circuit of a “follow the line” type robot with inductive sensors published in Radio...
With a unijunction transistor and a tunnel diode it is possible to obtain rise times of 1 ns with...
This receiver for listening to headphones and 2-battery power was found in Japanese documentation from the...