Message posted by Joerg (Webmaster) on March 25, 2012 at 12:24:13 PST:
Somewhat simplified, a trunking system is designed to make more efficient use of a given number of discrete frequencies. It consists of several sites, which each have a control channel and several (typically 4-12) voice or data channels. The control channel transmits a constant stream of digital data, which identifies traffic on the data channels. It tells the radios associated with the system which data/voice channel to tune into at any given time. The users of a trunking system are assigned a talk group, a number identifying their function (e.g. Nellis Tower, security etc.) Although all users of a system use the same channels, they only hear conversations in their talk group. Talk groups can transmit clear voice, or encrypted voice or data in various standards. Typiclly the conversation within a talk group "hops" from one frequency to the next each time a new transmission begins. So, if you were to listen to one of the voice channels with a conventional scanner, you would only hear unrelated bits and pieces of various conversations. All this is controlled by the control channel. Trunking scanners can decode the control channel, and "follow" converstaions within a talk group, so you can listen to the entire conversation. To make things a bit more complicated, a trunking system usually has several sites throughout the area of coverage. The system "knows" which users of which talk groups are within the coverage area of which site, and automatically transmits relevant talk group data on the sites as needed. Trunking systems are widely used by police departments, highway patrol etc. There are several trunking systems in use around the NTTR as listed in the attached link. Some systems can be decoded (lisened to) with trunking scanners such as the Uniden BCD-396T, others only show activity (talk group and radio ID), but cant be decoded. An example for the latter is the EDACS ProVoice system in use by, among others, Area 51 security. A special case of a trunking system, which again has several sub-standards, is the Have Quick system, which is now used by most players of the "Blue Team" during Red Flag and other exercises. It lacks a control channel, but instead relies on exact timing for the assignment of data channels.
In Reply to: Re: New trunking system around the NTTR posted by Brian L on March 25, 2012 at 11:30:31 PST:
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