From: lockhart@mothra.nts.uci.edu (Jack C. Lockhart)
Subject: Re: 800MHz Trunked Radio System Signals
Newsgroups: alt.radio.scanner
Organization: University of California, Irvine
Keywords: The Control channel
Date: 8 Jan 93 00:19:47 GMT

In article <1idqf9INN3cq@bigboote.WPI.EDU> gkd@wpi.WPI.EDU (Gregory K Doerschler) writes:
>In article <2B49E599.3879@news.service.uci.edu> lockhart@mothra.nts.uci.edu (Jack C. Lockhart) writes:
>
>>So, if the controller is programmed to perform ruthless pre-emption,
>>the control channel would reassign the pre-empted repeater to the unit
>>making the emergency call.  However, the possiblity and probability
>>exists that a part or all of the emergency call stations transmission
>>will be blocked.  This will occur if the pre-empted transmitting
>>station has captured the repeater.
>
>And murphy's law would probably dictate that the pre-empted station was
>some garbage collector in the middle of a 60 second diatribe about some
>house with too many trash bags in front of it.  There would likely be
>another channel free before the garbage collector unkeys.  The question
>is whether the system would be able to re-assign the unit with the
>emergency to one of the newly freed channels after it had already
>decided to pre-empt the garbage collector.
>
>                                     Greg


According to system engineers at Ericsson General Electric in
Virginia, and Motorola Communications in Illinois, the controller is
only able to determine if there is interference on a channel it has
assigned a radio to.

When a radio unit is pre-empted, it is pre-empted; there is no
waiting.  Sooooo, to answer your question: the only way the controller
would assign another channel to the emergency unit is if the garbage
collectors transmission created excessive interference on the
pre-empted repeater; and blocked the transmissions of the emergency
unit.  It takes the controller a certain amount of time to perform
this function.  Sorry, I didn't ask for a time reference.  In the mean
time, the emergency units transmission may be garbled.  Not very
conforting huh?

Again, this is why both system suppliers suggest that top of the queue
be used in lieu of ruthless pre-emption.

Sooooo, why was ruthless pre-emption created in the first place??????

~jack_

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