Wednesday, September 2, 2015

Cisco Voice: FXS Funky Digit Manipulation

I dont love problems that dont make sense.  I had this FXS module giving me a fit from the beginning of when I put it in place.  Every time you dialed out with the fax machine, the customer complained about it not getting where it needed to go.  So I showed up with my analog phone and sure enough, problems.  In fact, I would just pick up my phone, and it would dial a random four digit number.  Really odd.  It dialed 1119, then 4354, then 1161.  Every time was different.  Turned out the module was bad.  Time for an RMA.


  1. Great point...every network engineer's tool bag should include an analog phone. I use mine all the time.

  2. Shane, I always found the the whole FXS vs FXO module confusing. Can you give an example when you would need a FXO instead of an FXS module?

    1. Genetically speaking, fxo is for connecting to the phone company, like an analog line. Fxs is for a "station", like a fax machine or analog phone. There are other uses for these ports though.


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