EDACS Patch Tracking
From The RadioReference Wiki
EDACS systems sometimes bring several talkgroups together in a ‘Patch’. A patch might be used by a police agency at night to provide a single channel with a single dispatcher for a wide area. A patch is created when a single, temporary talkgroup substitutes for the original talkgroups. While the patch is running, which may be for hours or days, the original talkgroups cease to be used. If you were monitoring one of these talkgroups, you might think there was no traffic, but in fact the talkgroup was operating at the different temporary number.
If a talkgroup in your Scan List is patched, your scanner will continue to receive it under its new identity until the patch has ended. When a patch is being received, the radio will display PATCH ID, and will show the temporary common talkgroup plus all the included talkgroups in a cycling display. The scanners are limited to following one patch. The temporary talkgroups used for patches are usually found in AFS code 15-xxx, and sometimes 00-xxx.