Phone rang indicator light

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This, will detect the ring signal, energize the relay which latches up, and the LED comes on and stays on till you push SW.

                                                 ____ 
 tip o--CC---RR----o-D<-------o-----o------>D----^  ^----o-----+ 
                   |          |     |             SW     |     | 
                   |          |     |                    |     | 
                  \-/         |-    R||                  B-    LED 
                   Z          C     L|| ............     A     | 
                   |          |+    Y||          __.__   T+    R 
                   |          |     |         +--o   o---+     | 
                   |          |     |         |                | 
 ring o------------o----------o-----o---------o----------------+ 
     
    CC=.47 uF 200 V. capacitor 
    RR= 3k (depends on relay) 
    D = 200V diode  ( > < direction od diodes) 
    Z = 12 zener 
    RLY= any small relay 
    SW= normally closed switch 
    K = relay's contacts 
    BAT= 9 V. battery 
    R = 500 ohm (for LED) 
    C = some (10) uF capacitor 
  

Components are not critical. It should latch on first ring, if not reduce RR. If it took too long to deenergize, reduce the C.

Sources

  • Massoud Ajami (massoud[at]chemteca.sdsu.edu)

Category:Telephone

 

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