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
Network Group	Network Shelf	0	1	2	3	4	5	6	7
▼ Option 51C (0-15) / Option 61C (0-31) ▼
0	0	1	3	5	7	9	11	13	15
	0	0	2	4	6	8	10	12	14
	1	17	19	21	23	25	27	29	31
	1	16	18	20	22	24	26	28	30
▼ Option 81C IGS (0-159) ▼
1	0	33	35	37	39	41	43	45	47
	0	32	34	36	38	40	42	44	46
	1	49	51	53	55	57	59	61	63
	1	48	50	52	54	56	58	60	62

2	0	65	67	69	71	73	75	77	79
	0	64	66	68	70	72	74	76	78
	1	81	83	85	87	89	91	93	95
	1	80	82	84	86	88	90	92	94

3	0	97	99	101	103	105	107	109	111
	0	96	98	100	102	104	106	108	110
	1	113	115	117	119	121	123	125	127
	1	112	114	116	118	120	122	124	126

4	0	129	131	133	135	137	139	141	143
	0	128	130	132	134	136	138	140	142
	1	145	147	149	151	153	155	157	159
	1	144	146	148	150	152	154	156	158
▼ Option 81C FNF (0-255) ▼
5	0	161	163	165	167	169	171	173	175
	0	160	162	164	166	168	170	172	174
	1	177	179	181	183	185	187	189	191
	1	176	178	180	182	184	186	188	190

6	0	193	195	197	199	201	203	205	207
	0	192	194	196	198	200	202	204	206
	1	209	211	213	215	217	219	221	223
	1	208	210	212	214	216	218	220	222

7	0	225	227	229	231	233	235	237	239
	0	224	226	228	230	232	234	236	238
	1	241	243	245	247	249	251	253	255
	1	240	242	244	246	248	250	252	254

M1 System Sizes:

Option 51C : 1/2 Network Group: 16 Loops (0-15)
Option 61C : 1 Full Network Group: 32 Loops (0-31)
Option 81C with IGS : Up to 5 Network Groups (0-4): 160 Loops (0-159)
Option 81C with FNF : Up to 8 Network Groups (0-7): 256 Loops (0-255)

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

Network Cards:

QPC414 : ENET (Enhanced Network): Two Loops per card (max. 8 cards per network shelf)
NT8D04 : XNET (Superloop Network): One Superloop per card (max. 4 cards per network shelf)

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:

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.

Enter STAT l in LD 32 to check the status of one or all loops
Enter DISL l and ENLL l (in LD 32) to disable/enable a network loop.

Peripheral Signalling Cards:

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

Grp	Shelf	Loops	PSig
0	0	0 - 15	0
0	1	16 - 31	1
1	0	32 - 47	2
1	1	48 - 63	3

Grp	Shelf	Loops	PSig
2	0	64 - 79	4
2	1	80 - 95	5
3	0	96 - 111	6
3	1	112 - 127	7

Grp	Shelf	Loops	PSig
4	0	128 - 143	8
4	1	144 - 159	9
5	0	160 - 175	10
5	1	196 - 191	11

Grp	Shelf	Loops	PSig
6	0	192 - 207	12
6	1	208 - 223	13
7	0	224 - 239	14
7	1	240 - 255	15

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

Enter STAT PER x in LD 32 to check status of PerSig x (x = 0-9, Option 51C, 61C, x = 0-15, 81C with FIJI Ring).
Enter DSPS x and ENPS x (in LD 32) to disable/enable. Note, disabling a PerSig card will disable up to 16 loops!

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 to 8 Network groups with a dual ring fiber optic network replacing the intergroup cards and intergroup module, providing a maximum of 7680 timeslots!

Group, Shelf, Slots and Loops (Large System)

M1 System Sizes:

Network Cards:

Peripheral Signalling Cards:

Some background info - from the days before IP!

Group, Shelf, Slots and Loops
(Large System)