Sangoma Vega 100G/200G/400G Missing 0 on Caller ID

If you have a Sangoma Vega 100G, 200G or 400G gateway connected to a BT ISDN line, you might find sometimes that the Caller ID coming in on phone calls is missing the leading zero.  So you might receive a call that shows as being from ‘7123456789’ instead of ‘07123456789’.

The reason for this is that often an ISDN line doesn’t send the national or international dialling codes but instead a flag in the ISDN message called Type-Of-Number.  This flag can usually contains ‘national’ or ‘international’ as a value which is intended to tell the device connected to the ISDN line (i.e. an ISDN PBX) to add the correct codes to the start of the Caller ID depending on the location/country it is in.  The point of this is that these numbers might not be the same in different areas or countries.

To make the Vega put these numbers in, change the following settings found in the SIP -> Advanced SIP Settings page:

  • National Prefix = 0
  • International Prefix = 00

Then the gateway will add these numbers as long as the ISDN line includes the TON flag (which it should do if it is not sending the 0/00 in the Caller ID).