The US police siren circuit presented in this schematic is an alarm circuit which produce the sound of the US police .
This US police siren schematic circuit is based on the 555 multivibrator . To built this US siren circuit we can use two 555 IC’s or one 556 IC which contain two 555 chips in one package .
Synchronously with the siren sound a lamp will flash . The siren circuit is capable to drive loads with greater than 1 A current consumption for one or more lamps or a powerful loudspeaker .
Both 555 IC’s timers are configured to operate as astable multivibrators.
The first timer is configured to supply a rectangular signal of about 2 Hz at pin 9. The lamp is switched on and off by way of power transistor . The second 555 is configured to supply a square wave at pin 5 that drives the loudspeaker. The loudspeaker of the siren must have a value between 8 and 32 ohms .
The voltage needed for this siren can be between 5 and 15 volts .
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