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Biamp Systems

How to fix an analog telephone interface that won't dial

If you connect a standard POTS (Plain Old Telephone Service) line to the analog telephone interface in Audia or Nexia, you can expect to just pick up the line and dial a phone number. With the addition of digital PBX systems and ATA (Analog Telephone Adapter for VoIP systems), you might find that the telephone interface will pick up the line, you’ll hear dial tone but the system will never dial.

The reason this sometimes happens is that the telephone interface is set by default to wait for a valid dial tone before dialing.  If it doesn't detect a valid dial tone, it won't dial.  Some digital PBX's and ATA's generate what sounds like a dial tone, but the frequencies and/or levels of those generated tones may not be correct.

The easiest solution to this problem is to set the telephone interface to not wait for a dial tone before dialing.

Turning off "Wait for Dial Tone" 

  • Disconnect from your Audia/Nexia system. Wait for dial tone.GIF
  • Locate the Dialer block in your configuration and right click on it to open the Property Sheet.
  • Under DSP Attributes, look for a line that reads “Wait For Dial Tone” and change this field to “No”.
  • Reload the configuration and test again.  
  • Open the Control / Status block and verify that the voltage and current values are within the proper range - some ATA's do not provide the correct values. The typical voltage on POTS/PBX lines varies but one should expect between - 54V to - 40V when ON Hook (no dial tone) and - 20V to - 5V when OFF Hook. Current when ON Hook should be 0mA, when OFF Hook it should be around 23 to 35mA. Currents above 40mA can damage equipment over time.