Nortel DMS-100 Series Maintenance Manual page 130

3-14 SMS signaling
DDL message bits and field names
DDL bits Field name
Bits 1 –11 Concentrator field (C-field)
Bits 12–14 Spoiler bits (fixed pattern of
010)
Bits 15–17 Maintenance field (M-field)
Bits 18–19 Alarm data link field (A-field)
Bits 20–23 Protection line switch field
(S-field)
Bit 24 Spoiler bit field (fixed pattern
of 1)
Note 1: When a C-field is not available to send on the DDL link, the 8085 microprocessor sends an
idle pattern on the DDL link. The RCS also sends an idle pattern when no new C-field is present.
Note 2: When the M-, A-, or S-fields do not change between messages, the 8085 microprocessor
sends the previous field patterns. The RCS at the other end sends the same patterns. The 8085
microprocessor sends information to the SP only when a DDL field changes. The system does not
transmit idle patterns.
297-8231-550 Standard 09.01 August 1998
Explanation
To operate in Mode II, shelf groups AB and CD
use the C-field. This field carries information for
shelves A, B, C and D. The information
includes control of subscriber assignment and
deassignment to DS-1 channels, hook
transitions and activation of the PCM looping
test. Refer to Note 1.
Spoiler bits are inserted at preassigned
positions in the DDL to make sure that the DDL
cannot duplicate a signaling pattern.
The M-field on the A-link carries information for
all shelves, and controls card and customer
loop testing. Refer to Note 2.
The A-field on the A-link carries alarm and
system control information for all shelves.
Refer to Note 2.
The S-field on the A-link controls the switching
of the DS-1 protection link. Refer to Note 2.
Operating company personnel insert the spoiler
bit at the preassigned position in the DDL. This
action makes sure that the DDL cannot
duplicate a signaling pattern.