Using integrated circuit U450B manufactured by Telefunken can be made a very simple electronic buzzer siren. The integrated circuit U450B is a sequence of tone generator and can be used in various audio applications.
Because in this electronic buzzer siren circuit are amplified only square waves, maximum power output increase to about 3 W.
When switch S1 pressed, IC1 generates a sequence of three tones, whose frequencies can be changed by adjusting the trim C6.
The integrated circuit U450B is fueled by resistance R5. It has an internal stabilizer output voltage of 3.75 V. The size of R5 determine the amount of current to pin 3. Here is a current set less than 1 mA, because for lower values result in a distorted output signal.
The power supply must be able to provide about 0.5 A (in standby, the circuit consumes 6.5 mA).