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
00 13579111315
02468101214
1 1719212325272931
1618202224262830
10 3335373941434547
3234363840424446
1 4951535557596163
4850525456586062
20 6567697173757779
6466687072747678
1 8183858789919395
8082848688909294
30 9799101103105107109111
9698100102104106108110
1 113115117119121123125127
112114116118120122124126
40 129131133135137139141143
128130132134136138140142
1 145147149151153155157159
144146148150152154156158
50 161163165167169171173175
160162164166168170172174
1 177179181183185187189191
176178180182184186188190
60 193195197199201203205207
192194196198200202204206
1 209211213215217219221223
208210212214216218220222
70 225227229231233235237239
224226228230232234236238
1 241243245247249251253255
240242244246248250252254

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 conect 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.

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