Control Channel Only
From The RadioReference Wiki
Control Channel Only (CCO) is available in selected makes and models of scanners, when trunking Motorola systems and P25 trunking systems. For the older Uniden scanners that utilize banks and lists only 800/900 MHz trunking is supported; it is available on all bands where trunking is supported in the Uniden scanners that support DMA.
CCO programming is recommended for use in selected RS scanners starting with the Pro-93 in bands where Motorola trunking is supported and this includes all P25 trunking bands for the Pro-96/2096 and the GRE PSR-500/600 scanners. It enables the user to trunk a system by programming in only those channels that are utilized as a control channel, instead of having to utilize memory to program the entire system. This mode works for both analog and digital systems.
In the RR database, frequencies are marked in RED with a (c) for the primary control channel, and BLUE with an (a) for any alternate control channel. Be sure to program both primary and any alternate control channels. An example can be viewed here. In this case there are 4 control channels; 1 primary and 3 alternates.
- If the control channel should change, and it isn't one of the ones programmed in the list, trunking using CCO will fail, possibly making your scanner go deaf on a system. You can thus think of this a "mode to flag if any new control channels suddenly become active in the system."
- Harris Trunked Radio Systems may need all channels programmed since all can be the Control Channel
Older Uniden radios require that a band plan be programmed, as well as all the control channels, for CCO to work. RS/GRE radios including the New Whistler radios, as well as the newer DMA based Uniden scanners, only require a plan if it's an 800mhz rebanded system Motorola Type I or Type II. In addition, no plan is required when utilizing CCO in the 900 MHz band.
Scanners known to support CCO
For Uniden Band Plan Information visit the Uniden 800 mhz Rebanding article
Hints and Tips
If you need to trunk a multi site system (particularly if you are mobile, and moving from the coverage from one site (a) to the next (b), programming a dummy channel (c) will allow the scanner to move to another site(a,b,d) better during inactivity from the current site(a). The following illustrates the programming:
The dummy frequency (e) could be any valid frequency that is unused in your area (free of signal). Programming a used channel (c), in this position, could interfere with normal trunking. This tip works with the PRO-96 and 2096. (Thanks to user "fmon" for the tip and suggestion for the writeup) and could possibly work for other makes & models *amendment is needed here ***
Some of this information courtesy of the Control Channel only tutorial page at the Scan Control website