[TrunkCom] LTR... briefly

[Tom Swisher]

PhulesAu@aol.com wrote:
>  Can someone point me to a site for a brief description of the difference 
> between LTR system and trunked systems like Motorola's?

Briefly:

Motorola Smartnet and MA/COM EDACS systems use a dedicated control 
channel, where one frequency is dedicated to sending out control 
information for user radios to follow so they know what frequency to use 
when the talkgroup they are monitoring goes active. User radios monitor 
the control channel until an assignment is made, and they then go to the 
assigned frequency, where subaudible data (similar to CTCSS or DCS) 
holds them until the conversation ends.

Johnson LTR systems use what is called 'distributed control' where the 
control information is sent out on all system frequencies as subaudible 
data (again, similar to CTCSS or DCS). Each talkgroup is assigned a 
'home' channel, and monitors that frequency. If that frequency is tied 
up, the subaudible data tells the radios which channel to go to next.

Other than differing feature sets and the technical differences in how 
each system operates, they all serve the same purpose, to efficiently 
and dynamically allocate use of a limited number of frequencies among a 
large number of users.

Here is a good (but very detailed) technical description of LTR:
http://www.virtualcomm.com/cmn/faq/e/ltr.htm

Tom WA8PYR
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Tom Swisher, WA8PYR                        WA8PYR@columbus.rr.com
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