Mike's PBX Cookbook

Group, Shelf, Slots and Loops
(Large System)

Physical Meridian M1 Network Loop and Slot assignments. Superloop numbers are multiples of 4, and shown in bold.
With an NT8D04 Superloop card, faceplate connector J2 (lower) is for IPE shelf 0, connector J1 (upper) is for IPE shelf 1.

Network
Group
Network
Shelf
Network Shelf Card Slot
0 1 2 3 4 5 6 7
▼ Option 51C (0-15) / Option 61C (0-31) ▼
00 02468101214
13579111315
1 1618202224262830
1719212325272931
▼ Option 81C IGS (0-159) ▼
10 3234363840424446
3335373941434547
1 4850525456586062
4951535557596163
20 6466687072747678
6567697173757779
1 8082848688909294
8183858789919395
30 9698100102104106108110
9799101103105107109111
1 112114116118120122124126
113115117119121123125127
40 128130132134136138140142
129131133135137139141143
1 144146148150152154156158
145147149151153155157159
50 160162164166168170172174
161163165167169171173175
1 176178180182184186188190
177179181183185187189191
▼ Option 81C FNF (0-255) ▼
60 192194196198200202204206
193195197199201203205207
1 208210212214216218220222
209211213215217219221223
70 224226228230232234236238
225227229231233235237239
1 240242244246248250252254
241243245247249251253255

M1 System Sizes:

IGS = Intergroup Switch
FNF = Fibre Network Fabric (FIJI Ring)

Network Cards:

A Superloop (XNET) network card physically requires one card slot, though the adjacent slot must remain empty.
The slot next to an ENET card can be equipped with network (ENET, DTI, PRI), and non-network cards (ESDL, MSDL, etc).
IPE controllers (NT8D01) will typically connect to an NT8D04 XNET card, J2 (bottom): IPE Shelf 0, J1 (top): IPE Shelf 1

A network card arrangement example:

NT5D21 Core/Net Module

An NT8D04 may be placed in a Left (even) or Right (odd) slot (0-7). This is specified when defining the Superloop in LD 97.
Regardless of slot, Superloop numbers are always even and in multiples of 4. Eg, an NT8D04 in slot 3 is Superloop 4.

Peripheral Signalling Cards:

Each Network shelf requires a QPC43R Peripheral Signalling (PerSig) card, which extends the signaling bus to that shelf.

GrpShelfLoopsPerSig
000 - 150
116 - 311
1032 - 472
148 - 633
GrpShelfLoopsPerSig
2064 - 794
180 - 955
3096 - 1116
1112 - 1277
GrpShelfLoopsPerSig
40128 - 1438
1144 - 1599
50160 - 17510
1196 - 19111
GrpShelfLoopsPerSig
60192 - 20712
1208 - 22313
70224 - 23914
1240 - 25515

For example, if PerSig 0 is out of service, disabled or faulty, then loops 0 - 15 will not function properly.

Some background info - from the days before IP!

The Meridian M1 system uses TDM (time division multiplexing) time-slots to connect each party on an active call. These time slots are present on Network Equipment components called Loops. Each Loop has 32 time slots. A Superloop has 128 time slots (four Loops). 32 Loops are called a Group.

Up to 16 loops (or 4 super loops) can be equipped on a single network shelf. The back plane of a network shelf has 32 traces (or links), each of which carries traffic for a single network loop. 2-network shelves together (32 loops) max out the capacity of the back plane, and these two shelves constitute a 'Network Group' or 'Group'.

The Option 81C is a multi-group system because you can equip up to five Network groups (160 loops). This was later expanded (with a fiber ring) to 8 Network groups (256 loops) with a dual ring fiber optic network replacing the intergroup cards and intergroup module. This provided 7680 time slots for 3840 simultaneous conversations.