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Kai Klaas
02/10/12 17:06
Read: 442 times

#185830 - Phone lines...
Responding to: Mahmood Elnasser's previous message
Mahmood said:
I was investigating many methods of doing it, but since phone lines are available, I thought using the phone lines for both voice and DTMF signaling would be most suitable.

Yes, good idea, and way cheaper compared to optical fibers...

You could use transformers at both ends of phone line to provide galvanic isolation. But even opto coupling is possible, as Per mentioned. Then you could use the idle dc voltage on the phone line to power some little circuitry. But I guess using transformers will be much simpler and cheaper. Even ethernet is using tranformes, by the way.

But take care: In many countries the circuitry you connect to the phone line must electrically "look" like a standard telephone set, so that the phone line isn't loaded too much. So, you should have a look into the according standards...

Is it only one phone line you can access to transmit all the data and audio?

Kai Klaas

List of 12 messages in thread
long range RS-485      Mahmood Elnasser      02/10/12 01:51      
   Current loop?      Per Westermark      02/10/12 02:29      
   Repeaters?      Daniel Contarino      02/10/12 06:10      
   can you use repeaters?      Erik Malund      02/10/12 07:58      
      No      Mahmood Elnasser      02/10/12 14:10      
   Profibus people...      Kai Klaas      02/10/12 08:03      
      details      Mahmood Elnasser      02/10/12 14:24      
         just a note      Erik Malund      02/10/12 17:04      
         Phone lines...      Kai Klaas      02/10/12 17:06      
            phone lines      Mahmood Elnasser      02/10/12 23:06      
               Data collision      Kai Klaas      02/11/12 05:35      
   It just works at slow speeds      Oliver Sedlacek      02/14/12 05:03      

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