1.5 Administrator's Guide

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  3. 1.5 Administrator’s Guide
  4. Commissioning the unit
  5. Configuring Comma device ports
  6. Configuring devices for Fax / modem support
  7. Fax Over IP
  8. G.711 voice band data (ITU-T V.152)

G.711 voice band data (ITU-T V.152)

Com.X features that support voice band data for fax over IP are:

  • Automatic G.711 bypass for fax (see above)

  • The default configuration of Com.X SIP is constant latency (i.e. fixed jitter buffer)

  • Fax detection with automatic echo canceller disable is supported on analog/ISDN channels where echo cancellation may impair the fax signal

  • The A-law codec does not use DC removal filters

  • Com.X VoIP does not use Comfort Noise Generation or Voice Activity Detection

  • The SDP negotiation extensions (V.152 clause 7.1) are not supported in Com.X. However, a switch to G.711 A-law on re-invite accomplishes the clear channel requirement for voice band data, as described above.