Alarm Siren (ART435E)

A powerful siren can be used for various purposes. It can be used in alarm systems to chase away intruders or even to warn that the enemy has "fallen" into a trap.

This article was originally included, one of my books on espionage.

The siren that we give in figure 1 is for circuits operating with 6 tp 12V voltages and drives a loudspeaker with good power.


Figure 1 - Powerful siren
Figure 1 - Powerful siren


P1 adjusts the cadence of the sound, while P2 adjusts its pitch. The PTP42 power transistor must be mounted on a heat radiator while the speaker must be of good quality for greater sound yield.

It should preferably be mounted in a small acoustic box.



CI-1 and CI-2 - 555 - integrated circuits

Q1 - BC547 or equivalent - general purpose NPN transistor

Q2 - BD433 - NPN power transistor



P1 and P2 - 100 k - trimpots

R1 and R2 - 10 k - resistors (brown, black, orange)

R3 - 1k - resistor (red straight brown)

R4 and R5 - 4.7 k - resistors (yellow, violet, red)

R6 - 470 ohm - resistor (yellow, violet, brown)



C1 - 10 uF x 16V - electrolytic capacitor

C2 - 100 nF - ceramic or polyester capacitor

CS - 220 uF x 16V - electrolytic capacitor



FTE - 4 or 8 ohm - heavy speaker

Printed circuit board, integrated sockets, Q2 heat radiator, wired speaker etc.