tone multifrequency (DTMF) digit relay under Cisco Unified CME for SCCP FXS
ports is not supported.
SCCP FXS ports
under Cisco Unified CME control do not natively support RFC2833 DTMF-relay.
However, Cisco Unified CME can support conversion of DTMF digits to and from
RFC2833 DTMF-relay on its H323 and SIP interfaces when used with
SCCP-controlled FXS ports.
Cisco Fax Relay
is only supported on those Cisco IOS gateways and network modules listed in
Information About Fax Relay
Fax Relay and Equipment
The fax relay feature supports the use of existing customer premises
equipment (CPE) in voice networks by allowing legacy analog phones attached to
a Cisco IOS gateway to be controlled by Cisco Unified CME, and by providing
feature interoperability between analog and IP endpoints.
The voice gateway can be the same router that is being used for
Cisco Unified CME or it may be a separate router (for example, the
The fax relay feature facilitates replacement of the PSTN
time-division multiplexing (TDM) infrastructure with VoIP.
Feature Design of
Cisco Fax Relay
Cisco Fax Relay is a
proprietary fax relay implementation that uses Real-time Transport Protocol
(RTP) to transport fax data. It is the default fax relay type on Cisco voice
gateways and the only supported fax option for Cisco Unified CME 4.0(3) and
later versions. The fax relay feature provides enhanced supplementary feature
capability on analog ports connected to a Cisco integrated services router
(ISR) or Cisco VG224 analog gateway. Calls through the analog FXS ports are
controlled by the Cisco Unified CME system.
introduction of SCCP-enhanced features, SCCP gateways supported fax
pass-through only. SCCP-enhanced features add support for Cisco Fax Relay and
Super Group 3 (SG3) to G3 fax relay. This feature allows the fax stream between
two SG3 fax machines to negotiate down to G3 speeds (less than 14.4 kbps)
allowing SG3 fax machines to interoperate over fax relay with G3 fax machines.
The SCCP telephony
control (STC) application on the Cisco voice gateway presents the locally
attached analog telephones as individual endpoints to the call-control system,
which allows the analog phones to be controlled in the same way as IP phones.
With this capability, gateway-attached endpoints share the same telephony
features that are available on IP phones directly connected to
Cisco Unified CME. SCCP-enhanced features provide analog endpoint to analog
endpoint interoperability within the IP telephony network.
shows a multisite deployment of the fax relay feature in a Cisco Unified CME
voice service voip
name fax machine
Information for Fax Relay
The following table provides release information about the feature or features described in this module. This table lists
only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise,
subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco
Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Table 2. Feature
Information for Cisco Fax Relay
Cisco Unified CME Version
Fax Relay on analog FXS ports on Cisco IOS voice gateways under the control of
Cisco Unified CME.