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NT5K21 XMFC/MFE card Page 401 of 544
Option 11C and 11C Mini Technical Reference Guide
MFC signaling involves two or more levels of forward signals and two or
more levels of backward signals. Separate sets of frequencies are used for
forward and backward signals:
• Forward signals. Level I forward signals are dialed address digits that
identify the called party. Subsequent levels of forward signals describe
the category (Class of Service) of the calling party, and may include the
calling party status and identity.
• Backward signals. Level I backward signals (designated “A”) respond
to Level I forward signals. Subsequent levels of backward signals (B, C,
and so on) describe the status of the called party.
Table 123 on page 401 lists the frequency values used for forward and
backward signals.
Table 123
MFC Frequency values (Part 1 of 2)
Digit
Forward direction
DOD-Tx, DID-Rx
backward direction
DOD-Rx, DID-Tx
1 1380 Hz + 1500 Hz 1140 Hz + 1020 Hz
2 1380 Hz + 1620 Hz 1140 Hz + 900 Hz
3 1500 Hz + 1620 Hz 1020 Hz + 900 Hz
4 1380 Hz + 1740 Hz 1140 Hz + 780 Hz
5 1500 Hz + 1740 Hz 1020 Hz + 780 Hz
6 1620 Hz + 1740 Hz 900 Hz + 780 Hz
7 1380 Hz + 1860 Hz 1140 Hz + 660 Hz
8 1500 Hz + 1860 Hz 1020 Hz + 660 Hz
9 1620 Hz + 1860 Hz 900 Hz + 660 Hz
10 1740 Hz + 1860 Hz 780 Hz + 660 Hz
11 1380 Hz + 1980 Hz 1140 Hz + 540 Hz
12 1500 Hz + 1980 Hz 1020 Hz + 540 Hz