If I wanna to amplifier the Sound of siren circuit, may I connect it direct to power amplifier? or can I connect the siren circuit to the powered speaker?

 

An audio amplifier is designed to have a fairly low level AC input. The siren circuit has a fairly high level DC output.
The little speaker shown can be replaced with a power resistor having the same resistance and a coupling capacitor can feed an attenuator that can be the input to a power amplifier.

 

Input the power amp from the 51K resistor, and omit the transistors.

 

Input the power amp from the 51K resistor, and omit the transistors.

Nope. The output transistors make the sound frequency since they are a voltage-controlled oscillator. The multivibrator transistors feeding the 51k resistor slowly sweep the sound frequency up and down.

 

Get yourself one of these babies...

 

The air raid siren has a much lower pitch than the police cars and ambulances I've heard. The siren is huge and so is its battery.

 

Some (two-transistor) siren circuits will not work without the loudspeaker, the inductance and back-EMF negative spike is part of the oscillator. So putting in a resistor in place of the speaker can give odd results. 1,000-2,200uF capacitor on a two-transistor multivibrator is pretty funny. It will be very temperature and supply voltage dependent. OP should stick to the dual 555 timer Kojak siren, it looked the best.

FDNY uses Federal Signal Q-siren 123dB at 10 feet, motor uses 100A at 12VDC! No wonder I can't sleep.

 

Wow! I am a beginner not even new in electronics, I don't understand electronic concept that much, just do circuit which people did and ask advice, otherwise thanks very big for your help. I have completed all circuit I have been asking you,successfully they working.

just planning to make one I will post now.

 

You show a "wiring diagram" instead of a schematic. I found the original article and cropped its schematic. The schematic had a few errors and could work much louder with my modifications. The transistor had the wrong symbol and part number (it should be an NPN 2N3904.

 

Oops! Luckily I did not started this project yet, I will connect your modification in wiring diagram for your confirmation, so I will go ahead with this projects

 

Thanks Audioguru, hope everything is making sense now

 

You made errors with pin 3 of U3 and with Vhalf that I corrected.
I do not know why the switch shorts pin 7 of U1 to ground with a 100 ohm resistor R11.

 

You should use schematics instead of wiring diagrams, no matter how nice you think they are.

 

Oh, thanx a lot people for helping me out of this issues