Found in Radio Electronics from the 90s, this siren finds many variations on this site. The transistor must be equipped with a heat radiator.
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...