This attribute specifies the time after the end of fax traffic before
ingress G.711/G.726 fax idle suppression starts. It applies only if
modemFaxEncoding is g711G726 or faxRelayG711G726 and
negotiatedIgFisG711G726 is on.
faxHangoverTimeG711G726 is not used if this VoiceService is
running on a DS1V, E1V, 1pDS1V, 1pE1V and J2MV card.