Skip to main content

Finding information on setting up the Grandstream Handy Tone 503 (HT 503) analogue telephone adapter (ATA) for the UK on Virgin Media telephone network was a difficult and time consuming task.  An overall summary is available for FreePBX.  The specific settings were not covered and are summarised below.

One stage method channel dialing.  To make this work you need to configure the AC Termination Model setting correctly.  You would expect that this should be set to Country-based UK, but actually it should be set to Impedance-based 600R -- 600 ohms.

Incoming caller ID for Virgin Media is not the UK BT standard.  It is Bellcore.  The non-default settings that worked reliably and consistently are shown.  They were derived from the specifications.  Note the transport type.  The default transport type does work but requires an Asterisk restart whenever a configuration change is made, otherwise the caller ID is not presented to ringing extensions.

  • Caller ID Scheme: Bellcore/Telcordia
  • FSK Caller ID Minimum RX Level (dB): -46
  • FSK Caller ID Seizure Bits: 30
  • FSK Caller ID Mark Bits: 105
  • Caller ID Transport Type: Relay via SIP P-Asserted-Identity