This circuit was found in an American documentation from 1969. Indications of the used transistors are not given, but general-purpose types can be tested.
The CMOS 4046 integrated circuit is not very common today, consisting of a very efficient PLL for...
This circuit turns on an old cassette recorder when the telephone rings, thus enabling the...
This circuit can be used in panel signaling with common incandescent lamp. The lamp will flash at a...