This is the circuit diagran of two tone electronic siren. The scheme is simple and easy to built, it based on two ICs with different task: produce audio signal and amplify the audio signal.
List of Components:
R5: 10K (potentiometer)
C1 - C2: 10 uF
C3 - C4: 470 nF
C5: 10 uF
C6: 220 uF
IC1: Integrated Circuit TTL 7400
Z1: Zener 5 volts 1/2 watt
Speaker 8 Ω
The IC 7400 used to provide the ringtone signals., while the frequency of the sound produced is determined by the capacitors C3 and C4, and the modulation frequency is determined by the capacitors C1 and C2. The signal from the oscillator, implemented with the IC1 (7400), are applied to R5 which functions as volume control and amplified by the IC2.
If you want a siren with a higher volume, you can change the amp, you should only consider that the IC1 works with 5 volts, and reducing the supply voltage (R6 and Z1 should be change). For example, if you placed a amplifcador operate on 12 volts, R5 should be approximately 2.8 to 3 ohms.
The circuit published here is not tested yet, well-functioning or not is responsibility of the assembler.