From The RadioReference Wiki
EDACS SCAT (Single Channel Autonomous Trunking) systems operate on a single channel and alternate control data with analog voice traffic. While some scanners that have this programming option cannot track ID’s in this system, it can eliminate the control data so that all you hear is the voice transmissions when you monitor this type of system. 
Also, this excerpt from The Repeater Builder's Technical Information Page (PDF File)
SCAT is a unique application of a GETC shelf that is configured as an option to an EDACS Repeater. The SCAT option allows a single repeater to alternately perform the Control Channel or Working Channel functions. This extends the trunked operation into difficult areas such as ravines, tunnels, etc. and extremely low traffic density areas such as shopping malls. SCAT systems are available for all EDACS wideband configurations: VHF, UHF, and 800 MHz. The SCAT channel may be configured as stand-alone system or as part of a multisite trunking network.
Return to the EDACS page.