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Utah Communications Authority is no longer comprised of just 10 frequencies for each department. It's now comprised of multiple control channels and voice channels throughout multiple antenna sites that provide coverage to multiple agencies in the State of Utah. Some agencies are currently running under mixed radio system (trunked and analog) and are in the process of merging to a Project 25 Phase 1 and 2 system over the next few years in compliance with FCC regulations.
So the question asked what is the difference between Talkgroups, Control Channels, and Voice Channels?
In essence, a trunked radio system is a packet switching computer network. Users' radios send data packets to a computer, operating on a dedicated frequency — called a control channel — to request communication on a specific talk-group. The controller sends a digital signal to all radios monitoring that talkgroup, instructing the radios to automatically switch to the frequency indicated by the system to monitor the transmission. After the user is done speaking, the users' radios return to monitoring the control channel for additional transmissions.
This arrangement allows multiple groups of users to share a small set of actual radio frequencies without hearing each other's conversations. Trunked systems primarily conserve limited radio frequencies and also provide other advanced features to users.
A talkgroup is an assigned group on a trunked radio system. Unlike a conventional radio which assigns users a certain frequency, a trunk system takes a number of frequencies allocated to the system. Then the control channel coordinates the system so talkgroups can share these frequencies seamlessly. The purpose is to dramatically increase bandwidth. Many radios today treat talkgroups as if they were frequencies since they behave like such. For example, on a radio scanner, it is very common to be able to assign talkgroups into banks or lock them out, exactly like that of conventional frequencies.
Radio ID is the assigned number of that radio that is programmed into the system identifying what agency it belongs to and who is it specifically assigned to. (Example: 8001001 is the Radio ID for Clark County Fire Dispatch)
*Note: We do not suggest you buying an off-hand digital radio (Motorola, Tait, etc.) as a scanner and if you do, there are legal implications behind it, even if it's only strictly for listening purposes only. It emits a signal and radio ID where radio maintenance personnel can turn that signal off once detect as an unauthorized Radio ID and may lead to legal persecution and fines under state, county, and federal law if caught.