Comtech EF Data SMS-458B - Manual (Page 68)

SMS-458B Modem Protection Switch Revision 2
Theory of Operation MN/SMS458B.IOM
4–8
Table 4-3 describes the six command functions that can be executed.
Table 4-3. Relay-Remote Command Functions
Function Description
AUTO Executed only from REMOTE mode. This function places the switch
in the automatic mode of operation.
REMOTE Executed from any operating mode other than REMOTE; must be
executed before any other relay-remote function. This function
places the switch in the remote mode of operation.
BACKUP MOD 1 Executed only from REMOTE mode. This function is used to place
backup modulator 1 online when it precedes a target word or offline
when it precedes EXECUTE.
BACKUP DEMOD 1 Executed only from REMOTE mode. This function is used to place
backup demodulator 1 online when it precedes a target word or
offline when it precedes EXECUTE.
A valid command structure consists of words in the following order:
1. The START word begins all messages.
2. The COMMAND word follows the start word.
3. If the command affects the online or offline status of a prime modulator or
demodulator, the next 4-bit word must be the TARGET word. The format for the
target word is the BCD number for the prime modulator or demodulator. The
target word is not sent if the backup is to be taken offline or AUTO or REMOTE
mode is selected.
4. The EXECUTE word follows the target (or command) word.
The command words must be sent to the switch with no more than 10 seconds between
words for the switch to recognize a command. If the interval exceeds 10 seconds, the
M&C resets the word buffer and waits for the next START word.
If an incorrect word is sent, begin the message sequence again with the START word.
This word restarts the message sequence.