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Phone With Musical Songs(II)Circuit

2014-11-15 13:45  
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Phone With Musical Songs(II)Circuit
The ring call may make peoplenot able todistinguish which phoneis ringing when one office has many phones.There is a solution that changing the neighboring phone's ringing to different musical sounds.As shown in following figure is a circuit that can do so.IC3 of the figure is a music integration circuit.IC1 and IC2 are photocouplers.When the phone is on-hook,IC1 stops and IC3 outputs nothing,loudspeaker SP does not ring.When there is a call,LED of IC1 will be brilliant because of the AC ringing voltage and the photosensitive tube will be conducted to trigger IC3.The output signal is amplified by VT1 to make SP send out a musical sound.After the phone is off-hook, 6V~10V DC voltage generating within the phone makes IC2 runs, the multiple-unit tube of photosensitive tube and V12 is saturated.Then,output signal of IC3 is short,and SP stops ringing.At this time,the communication is available.The circuit will return to the original state.