User's Manual

SECTION I INTRODUCTION
SM 7063 07/97 1-2
1.1.1 CDU FUNCTIONAL DESCRIPTION
The CDU mounts in the locomotive cab; it connects to an antenna mounted on the roof and to the DC
power system (72 VDC nominal). Separate connectors are provided for connection to the locomotive Axle
Alternator (odometer), a Datalogging device, and a Diagnostic computer.
Since the CDU incorporates all displays, the warning beeper, and all controls on its front panel, it should be
mounted where it is highly visible and within easy reach of the locomotive operator (i.e., on the control
stand or in a console).
The CDU transmits and receives data to/from the End Unit using a UHF radio transceiver. The transmitter
frequency is typically 452.9375 MHz and the receiver frequency is typically 457.9375 MHz. When the CDU
receives a message from the End Unit, it processes the information and displays it on various LED
displays and annunciators. The CDU is typically in the receive mode of operation ready to accept and
display messages from an End Unit. When the COMM ARM key or EMERGENCY switch is pressed, the
CDU switches to transmit mode, sends the respective command message, and then immediately returns
to receive mode.
If the optional Arming feature (a security function) is enabled in the CDU, the Emergency transmission is
sent only if the CDU has been “Armed” to the ID code of its matched End Unit.
If the CDU is connected to the locomotive axle alternator, it can be configured for various odometer related
functions. These include the capability to display the distance traveled by the locomotive, a train length
function whereby the length of the train can be entered and stored and then be used as a preset distance
counter, and the display of train speed and/or acceleration. The CDU has built-in functions to allow
calibration of the odometer to compensate for locomotive wheel size variations. In addition, the CDU can
be configured to display odometer measurements in English or Metric units. Refer to Section III for
operating instructions.
An RS-232 serial port used for datalogger and event recorder functions is a standard feature of the CDU.
Whenever new information appears on the display or a transmission is received from the End Unit, the
data is transmitted to this port so that it may be stored in a computer, event recorder, or be directly printed.
The CDU also supports an RS-232 serial port for diagnostics, unit configuration, and download of software
upgrades. These are all performed via a standard DOS-compatible personal computer (PC).
As an additional safety feature, the CDU also displays the status of the emergency brake valve drive
circuitry used in the End Unit. It will show a “Valve Fail” alarm indication if a problem is detected.
1.2 DEFINITION of TERMS
The following terms and abbreviations are used throughout this manual:
EOT - End-o
f-Train: Refers to an End-of-Train telemetry system comprised of a Cab Unit mounted in
the locomotive and an End Unit mounted on the coupler of the last train car.
CDU - Communication D
isplay Unit: A two-way End-of-Train Cab Unit (e.g., CDU Model 6696).
SBU - Sense and Brake Unit - Any generic two-way End-of-Train End Unit capable of remote
Emergency Brake Applications.
HVM - Highly Visible Marking Device - The Marker Light portion of the End Unit; an FRA approved
flashing light used to mark the end of the train.