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This file is ment to be an overall look
at the GE MARKV trunking system.
The first thing to note abo the GE
system is that the repeaters are for all
purposes dumb. That is they have no
controllers intem. They funcion basic-
ally as a dedicated UHF repeater would
if the CTCSS tone where replaced wih
n audible tone and then notch filtered
out instead of useing a low pass filter.
This tone is calld te busy tone in the
GE system it is sent at a 3khz deviation
for 90 msec at the beginning of a cal
an there after at 1khz during all mobil
transmissions except during the select
call tones. The reeater send the busy
tone on all transmisstions except during
the retransmission of the select call
ones snt by the mobile.
The repeaters do two more things. They
send 90 msc of acquisition tone immdiatly
ollowing the first recipt of the 3khs
deviation busy tone in order that the
mobil recognizesthat an ctive repeater
has been hit. It will also time out and
drop the conversation aproxamatly 3 o 5
minuts after all repeaters become busy.
The mobil and cntrol staton radios
operate the same way.
The mobil has what smarts the system
needs to operate. Itfirst scansto find
a clear channel. It then sends 90 msec
of busy tone and listens for 90msec to
se if the aqusition tone is being sent
by the repeater. If it does not see the
tone it will scan foranother clear
channel and begin again. If the tone is
decoded the mobil will then send what is
calld a collectiontone for 90msec
times the number of channels in the
system plus one. This will allow nough
time for ll radios on the system not
talking to decode this tone and lock
onto this channel. he Mobil then trns-
mitts a two tone paging signal. All
cars decoding this paging tone will stay
onthis channel as lng as they continue
to decode a busy tone. All other cars
will revert back to scaning looking for
colection tone. In the event a car goes
thru a fade or is incapable of reciving
thebusy tone for any lgnth of time it
is dropped from the conversation and
cannot get back unless the ther cars
allow the ystem to drop out and
reinitiate the call.
I hope this explains the GEMARKV
ystem. If you have an questions don't
hesitate to contact me by EMAIL
Eric B. DeWitt
5025,1153
DOWNLOAED FROM P-80 SYSTEMS
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