2

For a long time I've been using a HylaFax server and an old external 56k serial port modem.

It has worked great on our POTS lines.

Recently we just upgraded our location and it now has an AT&T Fiber connection, and the telephone lines are all provided over the Fiber line.

Now, the old modem apparently isn't picking up when it gets an incoming call. I'm not sure why, but it's definitely some incompatibility between the new lines and the modem because I've tested the following:

  1. Old modem and Hylafax server still work fine on old POTS lines
  2. Old modem won't pick up incoming fax call on new fiber lines
  3. Standalone fax machine DOES pick up incoming fax call on new fiber lines

Why doesn't the old modem detect or answer the incoming call?

How can I get my old modem to work with the new lines?

Sven
  • 97,248
  • 13
  • 177
  • 225
Daniel
  • 1,594
  • 8
  • 26
  • 44
  • I see my original post was edited to remove my question about modem models. Are we not allowed to talk about hardware in Server Fault? – Daniel Oct 18 '18 at 20:25
  • 1
    Product recommendations are off-topic. – Sven Oct 18 '18 at 20:43
  • What hardware did AT&T give you? What hardware have you provided yourself? – Michael Hampton Oct 18 '18 at 20:53
  • The phone line comes from an AT&T router which has a breakout telephone patch panel connected via something that looks like an amphenol trunk cable. The router itself is connected to another box by ethernet which is the ONT/ONU. The only hardware I have provided relavent to this setup is the Hylafax server, the external fax modem, and the telephone cable. – Daniel Oct 18 '18 at 21:31

1 Answers1

2

This is a common problem with old phone devices (your modem) and newer telephone company hardware: the type of hardware provided by the telephone company doesn't provide enough ringing voltage for the modem to recognize an incoming call.

But first things first, if you haven't tried the working fax machine on that same phone line that the modem is connected to, do that. There might be a problem with that specific port.

If that works, you might try reversing the tip/ring wires. It's not out of the question that your modem could be sensitive to that, especially if the modem or the telephone company equipment (wrongly) grounds one of those wires.

Next, call the telephone company and ask them about it. They may have a solution for you. If not, you could buy a ring booster.

If you need a new modem, I doubt any manufacturer specifically lists "works with impotent telephone company equipment that doesn't generate high enough ring voltage". But there probably is a Hylafax community out there somewhere that does have a specific model recommendation.

longneck
  • 22,793
  • 4
  • 50
  • 84
  • The standalone fax does work on the same phone line. – Daniel Oct 18 '18 at 20:42
  • The phone line comes from an AT&T router which has a breakout telephone patch panel connected via something that looks like an amphenol trunk cable. The router itself is connected to another box by ethernet which is the ONT/ONU. – Daniel Oct 18 '18 at 21:26
  • Is this what you're talking about wrt ring voltage? http://www.sandman.com/ringvoltbul.html – Daniel Oct 18 '18 at 21:42
  • Yes, that's exactly what I'm talking about. But if you haven't tried it already, try reversing the tip/ring wires on the patch panel, if you can. It should be easy to do and won't break anything. – longneck Oct 19 '18 at 13:16
  • I don't think reversing the tip/ring wires is the problem. I called it a patch panel but it is connected to the router by a trunk cable with amphenol connectors on both ends. There is no easy way to reverse any wires there. And the telephone cable is just a standard factory-made cable. So, the only way for me to reverse those wires would be to make a custom "crossover" telephone cable. – Daniel Oct 19 '18 at 13:44
  • Reversing tip/ring could solve the problem. A common "mistake" that telco hardware makes is to put out pulsed DC instead of AC while ringing, and a common "mistake" that modems make for detecting ringing current is to use a half-wave rectifier. If the DC pulse is negative relative to the rectifier, the modem will never see the ringing voltage. – longneck Oct 19 '18 at 13:48