|PXML No. 47
APPROVAL No. NS/3343/123/G/452428 and NS/3343/123/G/452429 DDI
Cabinet layout (ISDX-S)
majority of the equipment defining the ISDX-S is in the form of printed
wiring cards, accommodated by two card cages in the ISDX-S and a single card
cage in the ISDX-MN which occupy the top sections of the robust, single bay,
sheet steel cabinet. Where the requirement is for a standard system of up to
96 extensions and 16 trunks, only the bottom card cage is equipped.
Removable front and rear preformed panels, fitted with individual locks for
maximum security, allow access to the card cages. The cabinet is mounted on
four castors, two movable and two locked, for ease of movement.
Forced air ventilation is provided by five fan units mounted in a tray
assembly, located under the bottom cage. Two thermal switches monitor the
temperature inside the cabinet such that should the temperature exceed 60
degrees an urgent alarm is raised and if 70 degrees is exceeded, the cabinet
power is automatically switched off. Air is drawn in through a foam covered,
steel mesh filter which is mounted horizontally across the cabinet floor
aperture. The filter is easily extracted for cleaning by removing the filter
cover at the bottom front of the cabinet, after releasing the two turn
In the ISDX-S, the power supply modules and double floppy disk drive (DFDD)
autoloader unit are mounted on a steel chassis in the lower portion of the
cabinet to give optimum stability. Access is again by removable locking
panels. Note that on refitting a panel, the lock is located near the
uppermost edge on all panels except the lower rear panel, identified by the
cut-out for the mains Input cable (AC version only), which must be refitted
with the lock at the bottom. The mains AC input to the AC powered cabinet,
is supplied via a fused spur, and is switched by the circuit breaker located
at the rear of the cabinet on the lower R.H. side. The DC powered version is
supplied from the power cabinet Mk 11 to bolted connections on terminal
Note: Earth straps are fitted at the cabinet doors.
Printer access is via the V.24 interface connector mounted horizontally on
the lower front panel, in the vicinity of the autoloader.
Four variants of the cabinet are available which provide a choice of AC or
DC, 2A or BA PSU systems. The advantage of the 8A PSU system is that the
shelf capacity may be increased since more power is available. The choice of
AC or DC power will depend on the site. The power for the AC version is
taken from the 24Ov mains supply. The DC version is powered from -50v
supplied by a power cabinet. The part number for each variant is as follows:
||AC, 2A PSU
||DC, 2A PSU
||AC, 8A PSU
||DC, 8A PSU
Where only the lower cage, of a two card cage system, is equipped, line PSU
L2, the intershelf bus, the shelf LIF backplane and all associated cabling, are
Cabinet layout (ISDX-MN)
In the ISDX-MN cabinet a single card cage is fitted in the bottom of the
cabinet. Forced air ventilation is provided by three fan units fitted between
the card cage and the power supply and autoloader units fitted above the card
cage. The mains supply is fed to the cubicle via a mains on/off switch and a
fuse at the rear of the cabinet. The DFDD autoloader is fitted at the top of the
cabinet. The cabinet part number for the ISDX-MN is 87111/13127/000.
Two card cages are mounted in the cabinet of the ISDX-S one above the other to
form shelves occupying the full width of the cabinet. A single card cage is used
in the ISDX-MN. The cards comprising the ISDX-S slide into grooved mouldings
fixed to the top and bottom of the cage, each cage in the ISDX-S having 33 slot
positions available. There are 27 slot positions available in the ISDX-MN.
In the ISDX-S the lower cage and, in the ISDX-MN the only cage, although forming
one physical shelf, is divided into two logical shelves, with the first seven
slots from the left, viewed from the front of the cabinet, referenced slots A to
G, logical shelf 0, and allocated to the computer control group cards. The
remaining slot positions numbered 02 to 27 on the ISDX-S and 02 to 21 on the
ISDX-MN are denoted logical shelf 1. On the ISDX-S the upper cage is denoted
shelf 2 and the slots are numbered 01 to 33 from left to right. Thus, the shelf
reference and slot position together, enable any card to be identified by a
unique physical address.
Multi-track backplanes mounted across the rear of the card cages connect the
cards into the system, the cards plugging into 96-way connectors mounted on the
backplanes to correspond to the card cage slot positions. The cards are shaped
to allow their P2 rear edge connector to slot into the lower backplane, which
occupies the full width of the cage, and their Pl connector to slot into the
appropriate upper backplane, when applicable.
Lower backplanes : P2
There are two P2 backplanes, the P2 control backplane is fitted the full width
of the bottom card cage and the P2 line backplane, the full width of the top
cage on an ISDX-S. The backplanes differ from each other in that the line
backplane accommodates only telephony and data groups together with an optional
miscellaneous group, whereas the control backplane also accommodates the control
group cards and the mandatory miscellaneous group. The parallel tracks of the P2
backplanes, which carry data between each shelf interface card and the relevant
telephony or data group, form the inter-shelf bus.
The various voltages provided by the line and ringer PSU to the terminal blocks
mounted centrally at the rear of the backplanes, are distributed via the
tracking and applied to the cards at the relevant pin (1 to 7).of the backplane
slot connector. The DSG and ALM terminal blocks, TB12 and TB16, located on the
R.H. rear of the P2 backplanes, are associated with the urgent alarm, initiated
by the closing of the thermal switch, should the cabinet overheat.
Certain cards operate as individual units to perform a defined function, whereas
others inter-act to perform a group function. A group backplane connects the
related members of the group, the card upper rear edge connector, Pl, slotting
into the corresponding backplane connector. In a number of cases the backplanes
are also used to connect preformed cables between the card and the Test Jack
Frame (TJF). Dummy backplanes are fitted to the card cage where gaps are left
between backplanes, to regulate the airflow within the cabinet.
In a two cage system (ISDX-S only), the cards occupying the top cage are linked
to the control group cards by the inter-shelf bus (ISB) which comprises two
entirely separate 64-way ribbon cables, located against the R.H. side panel of
the cabinet. 00 The cables differ in the wiring of the terminating connectors
such that one cable, coded 000 or X, is associated with the data present at the
A and C pins of an upper, Pl, backplane slot connector and the other cable,
coded 001 or Y, is associated with the data present at the A and B pins. Both
sets of data are carried in an alternate earth/signal format to avoid cross
Preformed cables provide the transmission path between interface cards of the
telephony and data groups and the TJF for connection to the external network.
The cables are connected into the rear of the relevant upper backplane slot
The control group cards are located in the bottom card cage, occupying slot
positions A to G, denoted logical shelf 0. The cards forming the group are:
||Megaword Memory and Controller
||Digital Switch Controller
The Shelf interface card located in slot 2, logical shelf 1 may also be
considered as a member of the control group as it connects into the Pl control
group backplane. A second Shelf interface card is located on shelf 2, slot 2,
when a two card cage system is installed, being linked into the system via the
Each card must occupy the correct slot position.
The Serial 110 interface and the Delta channel controller, physically occupy
slots E and F respectively but are not direct functional members of the control
group. The Delta channel controller card must be fitted for networking.
REF NUMBER NAME SLOTS CARDS
P2 06496/00X Control 33 All cards in the bottom cage
06540/001 Control 27 All cards
06498/000 Line 33 All cards in the top cage
PI 06494/00X Control 7 1 Megaword memory and
06538/000 memory controller
CPU 1; CPU 2; Serial I/O;
Delta channel controller;
Digital switch controller; Shelf I/F
06420/000 Shelf I/F 2 Top cage Shelf I/F. If supplied the
Rotary register occupies slot 1 but
does not connect into the Pl B/P
06416/00X Miscellaneous 3 General purpose I/O; Bypass;
Modem; Console I/F
06410/00X Trunk 6 Codec; Trunk controller;
4 x Trunk interfaces
06412/00X Extension 6 3 x Codec; 3 x Extension I/Fs
06414/00X 2 Codec; Extension I/F
06572/000 ISDT 1 ISDT interface, Modem, Terminal
server or ALI
06592/000 DLI 1 Digital link interface
Note:- indicates fitted to an ISDX-S only and # indicates fitted to an
The miscellaneous group comprises a combination of the cards listed below, the
exact combination being configured to suit the site requirements. The slot
position referenced is that which the card would occupy on an ISDX-S 9 all the
members of the group were required on a one card cage system. On an ISDX-MN the
second bypass card Is not fitted, and the slot is referred in brackets below.
|Common equipment card
||Slot 24 (18)
||Slot 25 (19)
||Slot 26 (20)
||Slot 27 (21)
The upper rear edge connectors, Pl of the card occupying slots 25, 26 and 27
(or 18, 19 and 20) plug into the 3-slot miscellaneous backplane. The remaining
cards may be directly linked into the system with the necessary cabling
connecting to the Pl connector on the card.
If a two card cage system is used the miscellaneous group cards can occupy any
of slots 25 to 27 of shelf 01 and slots 31 to 33 of shelf 02. Normally the
General purpose I/O card, Bypass card and Modem card occupy slots 25 to 27 of
shelf 01 and the Console interface card and Common equipment card occupy slots
32 and 33 of shelf 02. The Modem cards being wider must always occupy the slot
at the extreme right (slot 27 or 33).
In the ISDX-MN the miscellaneous group is fitted in slots 18, 19 and 20 with the
Modem card fitted separately from the miscellaneous group in slot 21 by using an
ISDT backplane for interconnection.
The remaining slot positions on the bottom card cage are normally occupied by
trunk and extension groups in the standard configuration of 96 extensions and 16
trunks. The top cage is used to accommodate trunk, extension and data groups,
the quantities, mix and slot positions being entirely dependent on the precise
site requirements. The remaining slot positions in the card cage on an ISDX-MN
are used for trunk, extension and data groups.
A trunk group is capable of handling sixteen channels, comprising six cards
connected into the system via the associated six slot trunk backplane. The group
must contain a codec and a trunk controller, the remaining four cards being
various combinations of exchange and IPBX interfaces as determined by the
An extension group comprises a codec and an extension Interface, each group
capable of handling sixteen channels, which may be all short line, all long line
or the specific twelve short and four long line mix. Two backplanes are
available to connect the cards into the system, one a two slot backplane
accommodating one group and the other a six slot backplane accommodating three
Double floppy disk drive (DFDD) autoloader
The DFDD autoloader is mounted on the cabinet lower front panel of an ISDX-S and
is a TEAC F35 GF double floppy disk drive fitted with system controller and disk
controller cards. The same autoloader unit is fitted at the top of an ISDX-MN.
The unit is normally loaded with the current system software disk and a back-up
disk, supplied separately. During system operation the contents of the current
system software disk are loaded into the memory of the ISDX-S and used to
control the system. By use of a DUMP command the contents of the ISDX-S system
memory can be copied onto the backup disk. This up-to-date dumped data can then
be used should a system reload become necessary.
The disks used by the ISDX-S are 3.5 inch MDF-2HD high density micro floppy
disks. They are supplied in plastic cases with spring loaded covers over the
disk surface. The disks must be handled with care to avoid corruption of the
stored data. The precautions listed below must be strictly observed:-
1. Check that the correct type of disk is being used.
2. Do not touch the shiny surface of the disk exposed in the jacket windows.
3. Do not bend the disk.
4. Replace the disk in the storage folder or file when not in use.