User's Manual

SECTION III OPERATION
SM 7063 07/97 3-21
3.10 ARMING the CDU to an END UNIT
If the CDU is operating in the two-way mode and is configured to use the “Arming” security feature, it is
necessary to first "authorize" the CDU to "talk to" the End Unit. This helps prevent undesired external
devices or people from intentionally or unintentionally activating the emergency braking function. This
process is called "Arming". An unauthorized or “unarmed” CDU can perform a Communications Link
Test with a End Unit but is not permitted to initiate an emergency braking command (i.e., its
Emergency Switch is disabled). Only after “Arming”, is an ID code considered to be an
"AUTHORIZED" ID Code. The figure below illustrates the Arming process.
To Arm a CDU/End Unit pair, the locomotive operator enters the ID code of of the End Unit into the CDU and radios the operator at the
end of the train that he is ready.
Figure 3.2 - Arming Process
“SYSTEM IS NOT ARMED”
OK, I’m ready
The operator at the end of the train presses the external TEST button on the End Unit and then releases it. When the TEST button is
released it, an arming request signal is sent by the End Unit. This message contains the End Unit’s ID and is marked as a “Request to
Arm” message.
When the Request is received by the CDU, the locomotive operator is prompted to proceed with the message “PRESS COMM / ARM
TO ARM” accompanied by the sonalert sounding for 5 seconds. The operator has 5 seconds to respond by pressing the COMM ARM
key. This initiates the “Command to Arm” message.
5 Second Beep
“PRESS COMM / ARM TO ARM“
Command to Arm
Arming Confirmation Message
“SYSTEM IS NOW ARMED”
When the Command is received by the End Unit, it responds with a “Arming Confirmation” message. When this message is received
by the CDU, it responds by declaring “SYSTEM IS NOW ARMED” to indicate successful completion of the arming process.
Request to Arm
“SYSTEM IS NOT ARMED”
Let’s Go!
Note. The Arming process must be completed within 6 seconds of the initial “Request to Arm” to be successful.
Figure 3-2. Arming Process