remote control equipment - Indian Railways Institute of Electrical ...

7.2.6.2The above sequence of message provides additional security by the check back
and execute messages, since undetected errors must occur in the control. select, check back,
and execute message in order to operate the wrong control device. Prior to transmission of
the above sequence a control operator performs a similar select-verify-execute-acknowledge
sequence via his control console.
Batch data transfers from master to remote include such data as parameters for report
by exception and parameters for locally controlled devices. This type of transfer is
accomplished by the sequence given below :-
MASTER - TO - REMOTE CONTROL MESSAGE
FUNCTION CODE DATA ADDRESS
FUNCTION CODE
REMOTE TO MASTER ACK MESSAGE
132
DATA ADDRESS
MASTER-TO-REMOTE CONTROL BATCH DATA TRANSFER MESSAGE
FUNCTION CODE DATA ADDRESS DATA
Notes :-
FUNCTION CODE
REMOTE-TO-MASTER ACK MESSAGE
DATA ADDRESS
1. Message establishment and message termination fields are not shown.
2. Special security precautions are required if a party line communication channel is
used, so that RTUs do not decode a batch data transfer message.
The purpose of first two messages is to prepare the RTU to receive the longer than
normal message. The third message transmits the data and the fourth indicates that the data
was correctly received at the RTU.