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TUCoPS :: Phreaking Technical System Info :: motorola.dox

Motorola Trunking System

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

This file is an over view of the Motorola Trunking 

The concept:
      Trunkilg 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.

             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 systIN` Ce vBI5 channels vCh Nel dedicated
to fhxJ*1 is 3600 baud on|y>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.

Whel 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:
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.



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