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This is a very simple circuit consisting of only two components,  a three pin ic UM66 or BT66 and a transistor BC548. this is a very easy method to make a calling bell. the circuit can be made without soldering also. i used a cassette box as outer covering    

Step 1: Parts List

1 x UM66
1 x BC548
1 x speaker 8ohm
2 x AA size battery
1 x battery holder
1 x common circuit board

Step 2: Circuit Diagram

complete the circuit according to the circuit diagram, its very simple circuit and works on two AA batteries, the music will vary according to the IC UM66   

Step 3: Conclusion

hope you enjoy the circuit................ please rate the instructable and comment if there is any doubts.Rechargeable battery should not be used if Speaker resistance is less than 8 Ohm and may burn the Transistor BC548 
It is a very good project specially for patients in bed who requires constant attention.
:)
What about a buzzer without the transistor??<br><br>thank you!<br>marC:)
BC 548 is used to amplify the sound if you don't use it, the sound will be low
This is so cool and cheap!Just the kind of project I like!<br>Have a look at my ibles!!!

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