mscDcmeProfileModemFaxEncoding 1.3.6.1.4.1.562.36.2.1.129.2.11.1.9

This attribute specifies how modem and fax traffic is encoded. Modem and fax traffic are identified by an inband 2100 Hz tone. Prior to the detection of a 2100 Hz tone, all traffic is handled according to voiceEncoding. If modemFaxEncoding is useVoiceEncoding, 2100 Hz tones are not detected on the channel. In this case, the channel does not differentiate between modem and fax traffic and voice traffic. All traffic is handled according to voiceEncoding. If voiceEncoding is g728at16 or g729at8, modem and fax calls will not work. If a 2100 Hz tone is detected and modemFaxEncoding is g711G726, all subsequent traffic during a call is encoded using pulse code modulation (PCM) defined by ITU-T G.711 or adaptive differential pulse code modulation (ADPCM) defined by ITU-T G.726. When the 2100 Hz tone is detected, traffic is initially encoded at the rate specified by maxModemFaxG711G726Rate. For the duration of the call, the bit rate can change due to network congestion. In this case, the minimum and maximum rates that can occur during the call are specified by minModemFaxG711G726Rate and maxModemFaxG711G726Rate respectively. If a 2100 Hz tone is detected and modemFaxEncoding is faxRelayG711G726, encoding switches to G.711 or G.726 at the rate specified in maxModemFaxG711G726Rate, exactly as it does if modemFaxEncoding is g711G726. Until a fax preamble is detected, the rate may fluctuate between maxModemFaxG711G726Rate and minModemFaxG711G726Rate due to network congestion, exactly as it does if modemFaxEncoding is g711G726. If a fax preamble is detected, all subsequent traffic during a call is demodulated and sent through the network as cells at the base rate of the sending machine. Supported demodulation methods are V.29 (up to 9.6 kbit/s) and V.27 (up to 4.8 kbit/s). The modulation and demodulation of fax traffic is called 'fax relay'. If a 2100 Hz tone is detected and modemFaxEncoding is faxRelayOnly, this channel does not wait for a fax preamble to switch to 'fax relay'. Instead, 'fax relay' is entered immediately. If modemFaxEncoding is faxRelayOnly, modem calls do not work on this Dcme. Therefore, this setting is only appropriate if modem calls are not made on the channel. The faxRelay feature is required to set modemFaxEncoding to faxRelayG711G726 or faxRelayOnly. modemFaxEncoding must have the same value at both ends of a Dcme. If modemFaxEncoding is not provisioned with the same values at both ends of a Dcme, the Dcme will not be able to carry the modem and fax traffic successfully.