March 2003
M2303-00-P00-805
5
1
Overview
The T2000-A76 AVL Modem is fitted as an options PCB within a T201X mobile radio. The AVL enabled T201X
radio collects and stores AVL data from a GPS receiver in its internal memory, which can then be relayed to
central control equipment.
A typical AVL system comprises:
•
a remote GPS receiver
•
a remote AVL T201X radio with a T2000-A76 fitted internally
•
a despatcher radio at the central control (CCDI capable T201X, Tait Orca or TRM )
•
a central control personal computer (PC) running an AVL application (e.g. SmartTrac)
The AVL application instructs the despatcher radio to poll the remote radio for AVL position and velocity data
which, when returned, is stored by the AVL application. The remote radio can also be set to emergency mode
where it periodically sends unsolicited AVL data to the despatcher radio.
The despatcher radios uses the Tait CCDI (Computer Controlled Data Interface) over-air command protocol to
communicate with the remote radio. CCDI commands containing short data massages (SDMs) are sent to the
remote radio by the PC AVL application. Each SDM contains a command which tells the remote radio to one
of the following:
•
send an AVL report
•
send database information
•
set the Group Delay Time
•
control the AUX line output
•
reset the radio
The despatcher radio is CCDI capable and connects to the PC by a serial line using standard RS232 signals.
The GPS receiver sends data to the A76 using the NMEA-0183 data transfer protocol. The A76 interprets the
RMC sentance from the GPS receiver.
Programming of the A76 is done using a special programming application from a PC via the serial port. Only
the Group Delay Time which enables group polling of radios can be programmed remotely.
Glossary
AVL
Automatic Vehicle Location
NMEA National Marine Electronics Association
GPS
Global Positioning System
RMC
Recommended Minimum (specific GPS/transit data)
SDM
Short Data Message
UTC
Universal Time Code
