Description: This attribute specifies how ingress modemFax and fax traffic are encoded.

Voice traffic is all traffic from the start of a call or speech until a 2100 Hz tone or call release. ModemFax traffic is all traffic after a 2100 Hz tone but before a fax preamble, speech or call release. Fax traffic is all traffic after a fax preamble but before speech or call release.

If modemFaxEncoding is useVoiceEncoding, all ingress traffic is treated like voice traffic and encoded according to voiceEncoding. If voiceEncoding is g728at16 or g729at8, modem and fax calls are not supported.

If modemFaxEncoding is g711G726, ingress modemFax traffic and fax traffic are both 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. The actual encoding and rates performed depends on congestion in the network and the minimum and maximum ingress modemFax rates in negotiatedIgRates.

If modemFaxEncoding is faxRelayG711G726, ingress modemFax traffic is encoding using G.711 or G.726, exactly as it is if modemFaxEncoding is g711G726. Until a fax preamble is detected, the rate may fluctuate between the minimum and maximum modemFax rates in negotiatedIgRates 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 modemFaxEncoding is faxRelayOnly, 'fax relay' is entered immediately upon 2100 Hz tone detection and modemFax traffic is treated like fax traffic. If modemFaxEncoding is faxRelayOnly, modem calls are not supported.

The negotiated ingress modemFax and fax encodings are available in negotiatedIgEncoding.

modemFaxEncoding cannot be set to faxRelayG711G726 or faxRelayOnly if this voice service is running on a DS1V, E1V, 1pDS1V, 1pE1V or J2MV card. The faxRelay feature is required to set modemFaxEncoding to faxRelayG711G726 or faxRelayOnly.

modemFaxEncoding must have the same value at both ends of a VoiceService. If modemFaxEncoding does not have the same value at both ends of a VoiceService, the VoiceService will be out of service. In this case, serviceFailureReason is mismatchedModemFaxEncoding.