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Difference between revisions of "Trunked Radio Systems"

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Revision as of 23:51, 6 February 2005

Overview

Please read this Trunking Basics overview first.

Motorola Trunked Radio Systems

Types

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Miscellaneous Information on Motorola Trunked Radio Systems


M/A-COM EDACS Trunked Radio Systems

Overview

EDACS was created by General Electric and then further engineered by Ericsson. The EDACS technology has changed numerous owners and now is currently owned by M/A Com (a Tyco Subsidiary)

EDACS is a lot similar to Motorola trunking. It provides for the same features yet has different names for them. Simulcast networks work the same yet EDACS networks, which are similar to AMSS networks, are all independent of each other but still interconnected. A radio is programmed with each system independently and selects each system based on control channel quality. Rather than have a site number a system is basically assigned a simple number to differentiate it.

Motorola uses a specific bandplan or a complicated frequency defined system to assign frequencies. EDACS uses what are called Logical Channel Numbers LCN. Rather than assign a frequency with a specific identifier, each frequency at a site is assigned a number between 1 through 26. When a channel announcement occurs it contains only the LCN. With this in mind each radio must be programmed with which frequency corresponds to which LCN.

Digital communications is also available for EDACS systems and exists in two different formats, AEGIS and ProVoice. AEGIS was the first format introduced and ProVoice was the last and current format. Neither one is APCO-25 compliant unlike Motorola’s ASTRO, which is. Also, neither AEGIS nor ProVoice can communicate with each other.

There are three different types of EDACS Control channels. The most common is the Wideband EDACS control channel, which operates at 9600 baud. There is also a narrowband EDACS control channel which operates at 4800 baud and primarly is used for wide-area EDACS systems in the 900 MHz band. Finally, there is the wideband EDACS "encrypted" control channel which is basically a variation on the standard 9600 baud wideband control channel. MA/COM's trademark name for this feature is called ESK (EDACS System Key).

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Links and Information

  • MA/COM Wireless Corp Homepage - The homepage for the MA/Com Wireless Corp, which designs, develops, and implements EDACS systems and technologies.
  • Racom Inc - Distributors of Ericsson EDACS equipment. See this link to their products and services page which has detailed information on Ericsson EDACS mobile and portable radios.
  • Hall Electronics GETECH Page - Lots of detailed information on progamming Com-Net Ericsson Radio equipment here. Cable pin-outs, connections, software versions etc can be found at this page for most of MA/COM's radio equipment.

LTR Trunked Radio Systems

Overview

LTR stands for "Logical Trunked Radio." LTR systems do not have a dedicated control channel like Motorola and EDACS systems. Each repeater has its own controller and all of these controllers are coordinated together. Even though each controller monitors its own channel, one of the channel controllers is assigned to be a master and all the other controllers report to it. Typically on LTR systems, each of these controllers periodically sends out a data burst (usually approximately every 10 seconds on LTR Standard systems) so that the subscriber units know that the system is there. The idle data burst can be turned off if desired by the system operator. Some systems will broadcast idle data bursts only on channels used as home channels and not on those used for "overflow" conversations. To a scanner user the idle data burst will sound like a short blip of static like someone keyed up and unkeyed a radio within about 1/2 second. This data burst is not sent at the same time by all the channels but happen randomly throughout all the system channels.

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