Detecting a telephone RING 2

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My computer is in the basement and this device tells me if the phone line is in use. I have inserted a N/O switch in the battery connection so that the batteries will last longer as sometime my sons spend a lot of time on the phone. Prior to using my modem I press the switch to find out if the line is busy.

                              2N3906         33K          2N3904 
             2.2 meg            /----------/\/\/\---+      /------+ 
                              |/                    |    |/       |    *** 
     Tip o--/\/\/-----+-------|   PNP               +----|  NPN   \    220 
                      \       |\                         | \      / 
                      / 330K    |                           |     \ 
                      \         |             +-------------+     | 
     Ring             |         |             |             |    --- 
         o--/\/\/-----+         |             O -           |    / \ Led 
            2.2 meg   |         |        3V                 |     | 
                      |         |             O +           |     | 
                      |         |             |             |     | 
                      +-------------------------------------+     | 
                                |             |                   | 
                                +-------------+-------------------+ 

Sources

  • Aurel Boisvert

Category:Telephone

 

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