Theory of Operation
SMS-758 Modem Protection Switch
4–8
MN/SMS758 Rev. 3
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.
Table 4-6 shows some relay-remote command examples.
Table 4-3. Relay-Remote Command Words
Input Lines
Command Word
REM3
REM2
REM1
REM0
START
C
C
C
C
AUTO
N
N
C
N
REMOTE
N
N
N
C
B/U MOD 1
C
C
N
C
B/U MOD 2
C
C
C
N
B/U DEMOD 1
C
N
N
C
B/U DEMOD 2
C
N
C
N
EXECUTE
C
C
N
N
C = Change of state. N = No change of state.
Table 4-4. Modem Target Words
Input Lines
Target Modem
REM3
REM2
REM1
REM0
1
N
N
N
C
2
N
N
C
N
3
N
N
C
C
4
N
C
N
N
5
N
C
N
C
6
N
C
C
N
7
N
C
C
C
8
C
N
N
N
C = Change of state. N = No change of state.
