'phone rang' indicator light

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From: Massoud Ajami

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.

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