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Comtech EF Data SMS-758 User Manual

Page 68

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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.