Super Group 3(SG3)

Super Group 3 (SG3) is a standard of fax machines that support speeds of up to 33.6 kbps through V.34 half duplex (HD) modulation and V.8 signaling.

Prior to Cisco IOS Release 12.4(4)T, SG3 fax machines could interoperate only over T.38 fax-relay and Cisco fax-relay networks with G3 fax machines, not with other SG3 fax machines, unless the fax machines were specifically configured to work at slower speeds or were configured for modem pass-through. The use of SG3 V.8 fax CM message suppression provides a gateway-controlled solution that enables SG3 fax machines to scale down without end-user interaction and without the extra bandwidth required by modem pass-through.

SG3 V.8 fax CM message suppression allows SG3 fax machines to interoperate over a fax-relay network at G3 speeds by blocking the SG3 V.8 CM message, or fax tone, from reaching the called fax machine. This causes the called fax machine to time out on the ANSam tone and scale down to G3 speeds by initiating V.21 negotiations.
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