UM 3561 is an excellent Siren generator IC widely used in Toy applications and Surveillance systems to generate different tones. It a ROM (Read Only Memory) IC which can be operated in 2 pen cells and it functions normally down to 2.4 volts. Using only a few components, it is very easy to construct a siren generator. The IC is designed to generate sirens like Police siren, Ambulance siren, Fire brigade siren and Machine gun sound.
Fig. 3: Image showing IC UM 3561 Tone Selection