FOUR IN ONE SIREN CIRCUIT

The UM3561 contains programmed mask ROM to simulate siren sound. Power consumption of IC is low.It is powered by 3 Volt. One NPN Transistor is used for amplification of audio signal.

This circuit gives sound of Police siren, Ambulance siren, Fire brigade siren and Machine gun sound. 
Part List :
IC UM3561
Resistance = 220 Ohms
Condenser 100Mfd
Transistor BC548
Battery Container 3V
Switches

UM3561 IC includes  oscillator and selector circuits so few external component is used for construction of four tone siren.

UM3561 is an excellent ROM IC that can generate Multi siren tones simulating Police siren, Ambulance siren, Fire brigade siren and Machine gun sound. This 8 pin low power IC can work down to 2.4 volts.

The UM 3561 is a low cost siren generator designed for use in toy applications. The IC has an inbuilt oscillator and tone selection pins. It is easy to make a siren generator with only a few external components. Only one external resistor and a speaker driver transistor are sufficient to make a simple siren generator.

Inside the UM3561

Inside the IC, there is an oscillator circuit and the frequency of oscillations is controlled by the external resistor connected to OSC 1(Pin 7) and OSC2 (Pin 8). A 220 K resistor will give satisfactory results. The oscillations thus generated will be then transferred to a control circuit which function based on the tone selection through the connections of SEL 1 (Pin 6) and SEL2 (Pin 1) . The control circuit passes the signal to an address counter and then to the ROM. The tone pulses thus generated will be available from the output pin 3. Since the sound is weak, an amplifier is necessary to get loud sound. A single NPN transistor will amplify the sound.

Pin 1 Tone Sel.2
Pin 2 Gnd
Pin 3 Output
Pin 4 NC- Used for testing purpose
Pin 5 +3V
Pin 6 Tone Sel .1
Pin 7 Osc 1
Pin 8 Osc 2

Make the following changes which can result in siren sound.