I assume you mean using FXS ports under SCCP control on an IOS gateway?
The SCCP Controlled Analog (FXS) Ports with Supplementary Features in Cisco IOS Gateways feature provides supplementary feature capability on analog ports connected to a Cisco Integrated Services Router (ISR) or Cisco VG 224 analog gateway. Calls through the analog FXS ports are controlled by Cisco Unified Communications Manager or by a Cisco Unified CME system. The SCCP telephony control (STC) application on the Cisco voice gateway functions as a proxy to translate call-control messages between the call-control system (Cisco Unified Communications Manager or Cisco Unified CME) and the voice gateway.
The STC application 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, organizations such as retailers are able to connect traditional analog telephones to a voice gateway and share the same telephony features that are available on IP phones directly connected to Cisco Unified Communications Manager or Cisco Unified CME.
http://www.cisco.com/en/US/products/ps6441/products_feature_guide09186a0080483a76.html
The only other SCCP function on an IOS router is the DSP farm based transcoding/conferencing feature. This feature uses the DSP resources installed in network modules on Cisco routers to provide voice-conferencing, transcoding, and hardware Media Termination Point (MTP) services -
http://www.cisco.com/en/US/products/ps6441/products_configuration_guide_chapter09186a0080541bf3.html
