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  3.   HARDWARE SYSTEM DESCRIPTION


  CENTRAL CONTROL COMPLEX (CCC) (Figure 2)

  3.01   The duplicated  CCC is mounted on two  adjacent bays.  Each
  CCC contains a group of four  units which act together to evaluate
  incoming messages, to  formulate the proper response  and to issue
  instructions  to  subsidiary  units.  The  four  units  and  their
  functions are:

       (a)  Central_Processing_Unit_(CPU)

            Is the  the central processor  for the DMS  system.  The
            CPU has  access to  memories where  stored programs  and
            network data are located.  The  processor uses this data
            to decide what  action is required to  satisfy the needs
            of the  network and  issues the  commands to  carry them
            out.

       (b)  Program_Store_(PS)_Memory_Module

            Is  exclusively  associated  with  one   CPU  and  is  a
            repository for the program instructions required by that
            CPU for call processing,  maintenance and administrative
            tasks.  The  PS associated with  the other  CPU contains
            duplicate program instructions.

       (c)  Data_Store_(DS)_Memory_Module

            Is  associated  with  one  CPU  and  contains  transient
            information on  a per-call  basis, as  well as  customer
            data  and office  parameters.   The  other CPU  is  also
            associated with a DS containing duplicate data.

       (d)  Central_Message_Controller_(CMC)

            Controls the flow  and priority of messages  between the
            other  units  of   the  CCC  and  the   Network  Message
            Controller (NMC) in the various Network Modules (NM), or
            the  Input/Output Controller  (IOC).   The sub-group  of
            three units (CPU, DS, PS) excluding the CMC, is referred
            to as the Central Control (CC).  Both CPU have access to
            either CMC which share the message load to the PM.












                  DMS-100 FAMILY SYSTEM DESCRIPTION
                  (c) NORTHERN TELECOM LIMITED, 1978


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  CENTRAL PROCESSING UNIT (CPU)

³ 3.02   The  CPU is a high-speed  data processor with  a microcycle
³ time of  111 nanoseconds and  a word length  of 16 bits,  plus one
³ parity bit.   It has two  independent parallel memory  ports.  One
³ port  (Program)   interfaces  with   external  memory   containing
  variable-length  instructions (PS),  while the  other port  (Data)
  interfaces with the data store (DS).  The CPU normally operates in
  duplicated matched  mode with  a mate  CPU, but  can also  operate
  singly. A 36MHz free-running clock  provides the basic CPU timing,
  controlling  register gating  and clocking,  emergency timers  and
  interrupt logic.  The 111-nanosecond  extendable microcycle period
  is derived from this clock.

  3.03   The CPU uses a register stack to manipulate data internally
  as well  as to and  from the data port.   The register stack  is a
  high-speed bipolar  store containing  frequently-used data.   This
  high-speed  store,   coupled  with   stack-oriented  instructions,
  contribute  to the  fast  execution speed  of  the  CPU.  The  CPU
  contains  the microstore  and microsequencing  logic necessary  to
  execute the program instructions.

  3.04    In addition,  the  CPU  contains the  following  functions
  required   only   for   dual   processor   operation:    matching,
  synchronization, inter-machine communication, fault indication and
  activity control.  A match exchange bus  (MEB) between the two CPU
  enables the  operation of one CPU  to be continuously  compared to
  that of  the other CPU.  Any  asynchronism between the two  CPU is
³ detected by maintenance circuitry and  appropriate action is taken
³ to change  to the alternative CPU.   The configuration of  the CPU
³ can  be controlled  and monitored  by manual  controls and  status
³ indicators which are  accessible or visible from the  front of the
  unit.


  MEMORY MODULES

  3.05   The  Memory Modules used  for the  PS and DS  functions are
  available in two configurations.  One  type provides Random Access
  Memory (RAM) in increments of 16K (K=1024) 17-bit words, while the
  other type has larger increments of  64K words.  The increments of
  RAM are in the form of  Metallic Oxide Semi-conductor (MOS) memory
  cards which are  plugged into the Memory Module.  A  maximum of 16
  active MOS Memory Cards, plus one  spare card, can be accommodated
³ per Memory Module.  A Memory Module occupies one shelf  in the CCC
³ bay.

  3.06   A  fully-equipped Memory Module of  the type using  the 16K
  MOS memory  cards, thus  has a maximum  memory capability  of 256K
  words.  The  Memory Module using  the 64K  MOS memory cards  has a
  maximum memory capability of 1024K words, or 1M word.





                  DMS-100 FAMILY SYSTEM DESCRIPTION
                  (c) NORTHERN TELECOM LIMITED, 1978


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  PROGRAM STORE (PS)

³ 3.07   For PS usage, using 16K MOS  memory cards, a maximum of two
³ Memory Modules can be used, occupying  both of the available shelf
³ spaces in the lower part of the  CCC bay.  Total RAM capability it
³ therefore 512K  17-bit words.   In this  case, the  DS is  located
³ elsewhere, as described  in the next paragraph.  For  a larger PS,
³ 64K MOS Memory Cards are used,  providing a maximum RAM capability
³ of 1M word, and requiring one Memory Module.


³ DATA STORE (DS)

³ 3.08   For DS  usage, the Memory  Module is equipped  with special
³ interface and termination cards, which permit the DS to be located
³ either in the lower shelf of the CCC bay (for a small DMS system),
³ or to be located in additional  adjaent bays.  These additional DS
³ bays, known as  Memory Extension (MEX) bays, have space  for up to
³ four Memory Modules per bay.  The  technology and packaging of the
³ DS Memory Modules is otherwise similar to that of the PS.  Maximum
³ RAM capability  per MEX bay is  1024K words, using 16K  MOS memory
³ cards, or 4M words using the 64K memory cards.


  CENTRAL MESSAGE CONTROLLER

  3.09     The  Central   Message  Controller   (CMC)   acts  as   a
  collector/distributor  unit  for  message  buffering  and  routing
  between the CPU and the Network  Message Controllers (NMC) or IOC.
  As  such,  it reduces  the  real  time  load  that the  CPU  would
  otherwise incur.  The CMC is duplicated  and appears on  both data
  port busses allowing access from either CPU.   The two CMC operate
  in load-sharing  mode. The side of  the CMC which  interfaces with
  the NMC and IOC is referred  to as the "peripheral side" (P-side),
  while the  side interfacing  with the  CPU is  referred to  as the
  "CC-side" (C-side).

³ 3.10   Included in each CMC is a  system clock which is the source
³ of timing  for the  network, PM  and IOC.    The stability  of the
³ system  clocl  is one  part  in  10-6.   The 8KHz  framing  signal
³ controlling the  32-channel time-division multiplexing  is derived
³ from  the  same   source.  The  clock  contains   two  independent
³ synchronized  timing  sources  derived   from  10.24  MHz  crystal
³ oscillators.  Only  one CMC  provides timing  for the  system; the
³ other is in synchronized standby mode.

  3.11   Up  to 64  Network Message  Controllers (NMC)  (32 in  each
  plane of  the duplicated  network) and  up to  6 IOC,  which drive
  visual  display units,  teletypewriters,  consoles, magnetic  tape
  units, etc., are connected to the P-side of each CMC.  The message
  links from  the CMC  to these peripherals  are two-way,  2.56 Mb/s
  asynchronous  ac,  data  channels  over   which  the  control  and
  signalling  messages flow.   The  CMC  distributes timing  to  the
  Network Modules (NM)  and, via the NM, to  the Peripheral Modules.


                  DMS-100 FAMILY SYSTEM DESCRIPTION
                  (c) NORTHERN TELECOM LIMITED, 1978


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  This ensures that the various components  of the system operate at
  the same rate or a multiple thereof.


  SWITCHING NETWORK (Figure 3)

  3.12  The switching network employs  four stages of time switching
  for  each voice  connection  between the  originating  PM and  the
  terminating PM.  The paths for each connection through the network
  are  assigned under  the control  of the  Central Processing  Unit
  (CPU).  The network  also distributes the control  messages to and
  from the PM  and the CPU.  The network is  fully duplicated, i.e.,
  Plane 0 and Plane 1, from the originating PM to the terminating PM
  to achieve the necessary reliability.

  3.13   Plane 0 and Plane 1 of the network each consist of a set of
  up to 32  Network Modules (NM), identified as  NM-0 through NM-31,
  each set  of NM forming an  identical and independent half  of the
  Network.  The  NM is the  major building  block of the  plane, and
  each NM has two sides, as follows:

       (a)  "Receive", Side A (incoming paths from the PM)
       (b)  "Transmit", Side B (outgoing paths to the PM)

  The  separate receive  and  transmit paths  give  the network  its
  inherent 4-wire characteristic.

  3.14   Each side  of an NM provides two stages  of time switching,
  the first stage performed by  an incoming crosspoint (IC-XPT) time
  switch and  the second  stage by  an outgoing  crosspoint (OG-XPT)
  time switch.   Each time switch has  eight ports (ports  0 through
  7), each port handling 32 channels  (30 voice + 2 message) between
  the NM  and PM.   Each side of  an NM  contains eight  IC-XPT time
  switches and eight OG-XPT time switches, usually referred to as an
  8X8  time switch  arrangement. The  full  capability of  an NM  is
  therefore as follows:

       (a)  Number of channels per port = 32 (30 voice + 2 message).
       (b)  Number of ports per time switch = 8.
       (c)  Number of time switches per side = 16 (8 x 8).
       (d)  Total  number  of  ports  per side  =  64  incoming  and
            outgoing.
       (e)  Total number of channels per time switch = 256 (8 x 32)
       (f)  Total number of channels per side = 2048 (32 X 64).
            Actually  1920  (30  X  64) voice,  and  128  (2  X  64)
            messages.










                  DMS-100 FAMILY SYSTEM DESCRIPTION
                  (c) NORTHERN TELECOM LIMITED, 1978


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  3.15    Since each  side  of an  NM performs  two  stages of  time
  switching, the  four stages of  switching through the  network are
  accomplished  by  connecting  the outgoing  ports  of  the  OG-XPT
  switches in the receive side of an NM to the incoming ports of the
  IC-XPT switches in  the transmit side of the same,  or another NM.
  The  connections between  receive and  transmit  sides are  called
  "junctors", and the pattern of connections between NM is dependent
  on traffic calculations.


  NETWORK SIZE AND GROWTH

  3.16   Since  Plane 0 and Plane  1 each require a  separate frame,
  each duplicated network  occupies at least two  frames.  Growth of
  the network  is accomplished by the  addition of NM in  each plane
  and rearrangements of the junctors.   The full network consists of
  32 NM  in each plane  and occupies  64 frames. It  provides 61,440
  voice channels in each direction in each plane (1920 channels X 32
  NM per plane = 61,440).


  NETWORK CONTROL

  3.17   Each NM  contains a Network Message  Controller (NMC) which
  exchanges messages with the Central  Control Complex (CCC) and the
  Peripheral Modules (PM) via the  Central Message Controller (CMC).
  Inputs to  the NMC from  the CCC come in  the form of  commands to
  locate  appropriate paths  through the  network,  to establish  or
  release network connections,  or to send a  maintenance code. Path
  selection is done  under control of software residing  in the CCC,
  based on a network map kept in  the Data Store (DS).  In the event
  of loss of the network map in the DS, the map can be reconstructed
  from  information stored  in the  NMC.   A fully-equipped  network
  contains 32 NMC per plane (NMC-0  through NMC-31), or 64 NMC total
  for both planes.


  DIGITAL CARRIER MODULE

  3.18    The  Digital  Carrier  Module   (DCM)  provides  a  direct
  interface between  the DMS digital  switching network  and digital
  carrier  signals  referred  to  as DS1,  which  in  North  America
  consists  of 24  2-way  voice  frequency channels,  time  division
  multiplexed onto a 1.544 Mb/sec bit  stream.  The DCM extracts and
  inserts signalling  information for  interfacing DS1  signals with
  the DMS-100 Family 32-channel, 2.56  Mb/sec speech links.  The DCM
  is a  self-contained shelf  having the  capability to  interface a
  maximum of five DS1 links (5 X  24 = 120 voice channels) with four
  30 voice channel (4 X 30 = 120) speech links.







                  DMS-100 FAMILY SYSTEM DESCRIPTION
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  TRUNK MODULE

  3.19    The Trunk  Module (TM)  encodes  and multiplexes  incoming
  speech from  a maximum of 30  analog trunks into 8-bit  PCM speech
  samples.   The  TM  combines the  samples  with  internal  control
  messages, as  well as the  trunk supervisory and  control signals,
  for  transmission at  2.56 Mb/sec  to  the network.  In the  other
  direction of transmission,  the 30 digital speech  signals and the
  two  control  channel  signals  received  from  the  network,  are
  demultiplexed and decoded by the TM into 30 individual channels of
  analog speech and associated signalling.  The TM also accommodates
  service circuits such as MF  receivers, announcement trunks, etc.,
³ either on dedicated TM or in common with analog trunks.


³ MAINTENANCE TRUNK MODULE, OFFICE ALARM UNIT

³ 3.20   Test  circuits are  accommodated on a  special type  of TM,
³ referred to as a Maintenance  Trunk Module (MTM).  Another module,
³ similar to the  MTM, accommodates alarm interface  circuits and is
³ referred to as the Office Alarm Unit  (OAU). Both MTM and OAU have
³ the capability of  interfacing 30 test or alarm  circuits with one
³ 32-channel, 2.56 Mb/sec speech link to the network.


  LINE MODULE

  3.21   For local applications, the Line Module (LM) provides voice
  and  signalling interfaces  between 2,  3, or  4, 32-channel  2.56
  Mb/sec  speech links  and  a concentration  of  up  to 640  analog
  subscriber  lines.  LM  are  installed in  pairs  on a  double-bay
  frame, with one LM on each  bay.  LM Controllers (LMC) on adjacent
  bays operate  as reliability  mates with  separate battery  feeds.
  The LMC contains the  PP function.  Each LM has access  to its own
  LMC  and  to the  mating  LMC  to  increase reliability.   One  LM
  occupies a single bay and has four line shelves and one LMC shelf.
  Each line  shelf contains five  line drawers which  accommodate 32
  line cards  each for a total  of 640 (4  shelves X 5 drawers  X 32
  line cards = 640) line cards per LM.


³ REMOTE LINE MODULE

³ 3.22   The Remote Line Modules (RLM) consist of specially-equipped
³ LM which  are located  remotely, but  which operate  as peripheral
³ modules  of  the DMS-100  Family  office  via DS1  carrier  links.
³ Special  interface  circuits  in  the   RLM  transform  the  usual
³ 32-channel speech link format at the  remote end to 24-channel DS1
³ format for transmission to the office.  The office end is equipped
³ with DCM  which transform the DS1  signals back to  DMS-100 Family
³ speech link format.  The RLM  provides an economical and efficient
³ method  of increasing  the  serving area  of  a  DMS-100 Local  or
³ DMS-100/200 Local/Toll office.



                  DMS-100 FAMILY SYSTEM DESCRIPTION
                  (c) NORTHERN TELECOM LIMITED, 1978


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  PERIPHERAL PROCESSORS

  3.21   The  Peripheral Processors in the  PM (DCM, TM or  LM) each
  consist  of  a  microprocessor with  associated  Read-Only  Memory
  (ROM), Random-Access  Memory (RAM) and  Arithmetic and  Logic Unit
  (ALU).   The ROM  contains "firmware"  (fixed instructions)  which
  control  the microprocessor  as it  performs  the following  local
  tasks:

       (a)  Scanning  the  trunk  or  line  interface  circuits  and
            detecting a change  of state on the  associated trunk or
            line transmission facility.
       (b)  Timing of call processing functions.
       (c)  Collecting and storing dialled digits.
       (d)  Generating digital tones.
       (e)  Sending and receiving signalling and control information
            to aid from the CCC.
       (f)  Providing integrity  checking of  network paths  between
            connected PM.


  INPUT/OUTPUT CONTROLLER

  3.22   The Input/Output  Controller (IOC) operates similarly  to a
  PM, but its  PP communicates directly with the CMC  instead of via
  the  NMC.  Each  IOC accommodates  up to  nine device  controllers
  (DC), each  of which  has its  own subsidiary  PP.  There  are two
  types of DC,  one provides an interface to one  magnetic tape unit
  on which system  data such as Automatic  Message Accounting (AMA),
  or Operational Measurements (OM) are  recorded.  The other type of
  DC is  a multi-purpose controller  capable of  handling interfaces
  with up to four I/O devices.  The configurations of the four ports
  on the  multi-purpose DC  can be  set, via  software commands,  to
  match  the characteristics  of the  I/O devices  (TTY, VDU,  etc.)
  connected to the ports.

  3.23    A   special  type   of  IOC  is   used  for   the  DMS-300
  (International)  switch application,  in addition  to the  regular
  type of  IOC.  This  special IOC provides  an interface  to handle
  signalling messages in  No. 6 CCITT format.   The common circuitry
  and PP of  this type of IOC are  the same as the  regular IOC, but
  instead of DC, the IOC is equipped with No. 6 Signalling Interface
  cards. In this  configuration, the IOC is  referred to as a  No. 6
  Signalling Shelf.











                  DMS-100 FAMILY SYSTEM DESCRIPTION
                  (c) NORTHERN TELECOM LIMITED, 1978