%%%%%%%- MOTOROLA TRUNKING SYSTEM  -%%%%%%% 


	This file is an over view of the Motorola Trunking system.


The concept:

	Trunking is a means of having a large amount of Two way radio
users on a few channels without the bother of waiting for the other
users to clear a channel or as in conventional repeaters having all
other users on that channel able to moniter your voice traffic.
Interconnect to the telephone lines available as an option.This
allows phone calls to be made and recieved as well as dispatch.



THE EQUIPMENT:

	Trunked systems in the U.S. currerently are all in the 800 MHZ
range with the systems being repeater type systems. The main
differences is where to put the logic and control package and what
type of signalling system used.

	The MOTOROLA system was designed with the logic in a central
control unit located at the base repeaters and a primarily digital
format for signalling between mobiles and the system.  Data at 3600
baud is primarily used, also used is 150 baud and 3 tones (1800
hz,105 hz,and 163 hz).

Terms used:

	For our uses we will suppose that the user is a rapid package
delivery service with roving supervisiors,roving expiditers,standard
delivery people and you the Boss.


FLEET: The entire group of mobile units and portables.

SUBFLEET: A user defined section of mobiles,portables, and or base
units. A subfleet can be just the delivery people and a base;or the
Boss and his supervisiors or any other combination needed. The mobile
units can be fixeF to one w be able to move bexvT WyB m to a max of
20 channels with 305 fleets.

	We will call on a basic system. IN C e vBI5 channels vChannel
dedicated to fhxJ*1 is 3600 baud only>C eL |he mJ!1 is turned on it
scans for the continuously transmitted background data stream.  this
stream also contains the system Id.  The mobile if assigned to this
system will decode the Id and sit on this channel. If a conversation
for this mobile is in progress then the mobile decodes the data and
joins the in progress conversation.

	When the mic button is depressed the mobile sends on the data
channel a request for service(known as the inbound signaling word
,ISW.).  The ISW contains the following ildormation: Fleet,Subfleet,
and Unit ID.

	The system hears the request and checks all channels for an
activity. When it finds one it sends back on the data channel the
following: FLEET,SUBFLEET,UNIT ID,AND CHANNEL INFORMATION.  This is
known as an Outbound signalling word,OSW.

	The OSW will send the mobile to a channel by programming its
synthesiser.If all channels are busy the OSW will cause a busy tone
to be heard and a busy lamp to light. The request will be held and
the system will call back when a channel is available.

	With the requesting mobile now on the voice channel the system
still sends the OSW on the data channel and sends a 3600 baud
handshake on the voice channel.The handshake has Fleet, Subfleet and
Unit Id in it.

	When the requesting mobile decodes the handshake it responds on
the voice channel with 80 msec of 1800 hz tone.This tells the system
that it is on the voice channel.

	The system responds by changing the handshake from 3600 to 150
baud data using less devation.  The 150 baud has in it Fleet and
Subfleet data.  The system now sends all other mobiles that are in
the same fleet and subfleet to that voice channel. When they arrive
they decode the fleet and subfleet data and unmute the speaker to
recieve the voice message. OSW still being sent on data channel

	The requesting mobile now swipches po sen`ing the subau`able
connect tone (105 hz) while voice is being transmitted.

	The system hears the connect tone and hohds the channal for that
subflaet.

	When the requesting mobile unkeys for the first tiie ip sends a
200 msec of disconnect tone(164 hz).  It also hears the 150 baud data
and uniutes the speaker.

	The disconnect tone starts a tiie oqt tiiar in the systei.

	All iobiles now on the voice channel may use the channel.  Each
time any mobile keys up it sends only connect tone.  This tone talls
the system that the channel is in use and resets the time out timer.

	When the conversations are done the timeout timer will expire in
the system causing a disconnect data word to be sent on the voice
channel.This mutes the speakers of all the units on that voice
channel and all units return to the data channel.  The OSW on the
data channel is dropped.

	The system will put that fleet id in the recent user queue.It
will have first call on the system instead of a new request by a
different subfleet.  This is to ensure no waiting of a channel in the
middle of a voice message if someone lets the system drop out.

	This system has a lot of nifty other features including what I
call the Boss call and the call from on high. As this is long enough
already,I will save them for another time.

	If you have any questions leave a msg in the forum in section 3
and I will be glad to give you any information I can.


JOE BARTLETT 70675,306  ALT.SYS.COMS
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