This circuit is from an old American documentation from the 70s. Transistor 2N3904 can be replaced by BC548. The relay must have 100 mA of maximum current.
The voltage gain of the circuit shown in the figure is 10 times. This gain is given by the ratio...
This circuit, from an old Argentine publication, uses a slightly different symbology than we are...
In this circuit we have two oscillators, one controlling the other, using the 4 NAND gates of the...