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Remote telephone line extension bell ringer circuit

2016-02-06 14:16  
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The telephone-line extension bell ringer shown will enable you to add a remote ringer in your garage or some other area where a ringing telephone cannot be heard Up to Four ringers can be used on a single telephone line,and a remote bell can be used 100 feet or more away from the unit.The two neon bulbs will light when more than 100 V is across the ringing circuit. The bulbs provide line isolation between the unit and the telephone line. Finally, they act as a voltage divider for the bridge rectifier made up of D1 through D4. That voltage divider creates a positive voltage that is then applied through D5, is filtered by  R2 , R3, and C2, and causes Q1 and Q2 to conduct.When that happens, triac  TR1  is fired through the optical coupler IC1; this turns on the triac, which applies 110 Vac to the load.The optoisolator and triac then turn on, applying power to the remote bell through a doorbell transformer.An extension bell or extension ringer is a device that generates a sound to indicate an  Extension bells may be louder than ordinary telephone ringers.