Click for Mitel Web Site


PXML No. 76
NS/1412/123/D/022046 for systems without DDI & NS/1412/123/F/451637 for systems with DDI.


The Mitel SX-2000 is a digital integrated communications Private Automatic Branch exchange (PABX) system. The SX-2000 is called an Integrated Communications System because it can switch telephone calls and data connections between terminals and / or computers. The capability to handle both voice and data is one reason why the SX-2000 is economical and flexible. Only one system is needed for both tasks, to connect a telephone and a terminal to the same line, allowing rapid office reorganisation without the need for rewiring.

The SX-2000 consists of the following subsystems and equipment:

  • Fibre optic cable distributed equipment cabinets that house the central processor and common control elements of the system and circuit cards;
  • The software that controls the system; An integral hard disc drive that stores the system software and the working copies of the system data;
  • A cartridge tape that is used for loading and making backup copies of the system software and data, including optional software;
  • One or more Superset operator consoles:- These can be screen based or LCD display consoles offering unrivalled facilities including a powerful programmable telephone directory. The console can be used to perform Moves and Changes;
  • Extension telephones, both standard and the Superset family of digital telephones:- Whilst most approved telephone instruments can be connected to the system. Feature telephones not supplied by MITEL may not have access to all features and facilities. MITEL recommend that telephones that are not supplied by us are tested for use with the SX-2000 prior to purchase.
  • Printer to provide the system manager with a record of system data, traffic information, including calls to and from individual extensions.
  • Datasets to enable telephone users to make and receive data transmissions;
  • Optional maintenance terminal and printer, which the maintenance engineer can use for fault diagnosis and reprogramming;
  • System Fail Transfer circuits that ensure a telephone service to predetermined extensions in the event of a power supply failure (beyond the duration of the optional stand-by power equipment);
  • A Test Jack Frame that provides a distribution point for the system wiring.

Note:- the light grey cabinets will not fit into a standard 19 inch rack as they are wider than 19 inches.  The later dark grey cabinets have a reduced width for the casing, but not the two front doors.  The dark grey cabinets can therefore be installed into a 19 inch rack, on a shelf, but the front doors will not go into the rack and will stand proud on the frame.

Tailoring the SX-2000
Within the limits of their capacities, every SX-2000 installation is unique in that the purchaser can specify a system that will meet their needs.
A number of ways of tailoring an SX-2000 are possible, including:

  • Providing the required number of telephones, operator consoles and other equipment;
  • Distributing and locating equipment cabinets adjacent to telephone communities;
  • Selecting system options and features to provide the desired service;
  • Provide each telephone user with system features that are most; appropriate to their function;
  • The ability to change numbers and locations of equipment and options and features to suit organisational change.
  • The SX-2000 can accommodate a number of different applications such as, a General Business system, a Hotel system, an ACD system or a Utilities based system.
  • The SX-2000 can be linked with other PABXs to form a network; The network can consist of analogue private wires and digital DPNSS links.

Technical Description

A Mitel SX2000 LIGHT will consist of a Control Cabinet (single or duplicated processors) which may have associated Peripheral Cabinets, Digital Service Unit (DSU) Cabinets and ISDN Server Cabinets.

Fibre optic cables connect each Peripheral Cabinet and DSU Cabinet to the Control cabinet.  The system is over wise known as the SX2000FD, FD for fibre distributed.

Peripheral Cabinets and DSU Cabinets can be located up to 1 Km from the Control Cabinet allowing peripheral resources such as lines (extensions), trunks and digital service applications (DPNSS/DASS2), to be physically distributed.

For example, several Peripheral Cabinets might provide telephone services to office areas, where the SX-2000 fibre cables can share the same routing as that of Fibre LAN(s).

Each Peripheral Cabinet will connect to the Control cabinet via a fibre optic (twin) cable. Copper cables from extension telephones will terminate at a Peripheral Cabinet avoiding the need for copper wiring between floors or lengthy cable runs to the PABX room.

Control Cabinet
Each Control Cabinet can support up to 11 Fibre Interface Modules (FIMs). Peripheral Cabinets require one fibre cable pair, allowing a maximum of 11 Peripheral Cabinets that will provide a total of 2112 ports. Each DSU Cabinet requires two fibre connections. This will allow a maximum of 6 DSU Cabinets that will provide 1320 digital trunks. Any mix of Peripheral and DSU Cabinets is permitted, allowing a range of configurations from a 1320 trunk Tandem switch to a 2112 extension port PAX. The SX2000 LIGHT is a flexible, powerful system that can meet almost any customer configuration requirement.

OPTION 1 - Redundant
The dual processor SX2000 LIGHT Control Cabinet has back-up main control redundancy, with independent power supplies. If a component fails, system operation will not be affected.

OPTION 2 - Non-Redundant
A single processor option provides full system functionality without the redundancy facilities.

A single processor SX2000 LIGHT Control Cabinet can be upgraded to dual processors at any time during the life of the system.

Main Control Components

  • Duplicated 200 Watt Power Supplies
  • Duplicated Power Modules
  • Duplicated Main Control Card
  • Duplicated RAM Card
  • Duplicated Circuit Switch Matrix
  • Control Resource Card Duplicated Hard Disk Drive
  • Cartridge Tape Unit Control Panel
  • Fibre Interface Modules (maximum 11)
  • Control Backplane

SX2000 LIGHT Maximum Hardware Capacities

Cabinets 12
Hard Disk Unit 2
Peripheral Interface Cards 132
DSU Cards 22

SX2000 Main Cabinet Redundant (Dual Processor)

OPTION 3 - Microlight
The SX2000 MICROLIGHT main cabinet consists of the following components: Main Controller Card; 8 Peripheral Card Slots; 4 DSU/Fibre Interface Card Slots (FIMs); Hard Disk Drive; Cartridge Tape Unit; Control Panel; Power Supply and Power Converter; Peripheral Switch Controller.

The 4 DSU Card Slots can alternatively accommodate Fibre Interface Modules allowing a maximum of 4 Peripheral or 2 DSU Cabinets to be added. The SX2000 MICROLIGHT will support up to a maximum of 768 ports. Any mixture of Peripheral and DSU Cabinets is permitted allowing a range of configurations from 240 trunk tandem switch to a 768 extension port PAX.

The SX-2000 MicroLight Main Cabinet has eight peripheral slots, each having 16 circuits, giving 128 ports.

In addition, there are four Digital Service Unit (DSU) / FIM slots that can be used for DSU cards or fibre cable interface to another cabinet.  If the fourth DSU / FIM slot is used, the eight peripheral card slots within the Main Cabinet cannot be used.

DSU slots are typically used for 2 Mb digital trunk services (2 per card) or Comms Processor cards for HCI type applications.

Each Peripheral Cabinet provides 12 slots, each slot containing 16 ports a total of 192 ports for each Peripheral Cabinet.

Any peripheral card can be installed in any of the available 12 slots at any time without interrupting the integrity of the system.  The software supports configurations up to the maximum sizing without the need for re-configuration.

DSU cabinets can be supported to provide digital trunk interfaces, conferencing circuits, or advanced tone detectors as optional units.  TWO DSU cabinets maximum can be supported.  The system can support any mix of Peripheral and DSU cabinets within the specified parameters.

SX2000 MICROLIGHT Maximum Hardware Capacities

  • Cabinets : 5
  • Hard Disk Unit: 1
  • Peripheral Interface Cards: 48
  • DSU cards: 8
SX2000 Microlight Main Cabinet

The SX-2000 MicroLight will support the following configurations:

Please note that ½ x DSU is a standard cabinet with a single fibre connection.  One x DSU is a standard cabinet with two fibre connections.  The SX-2000 MicroLight Main Cabinet can support four fibre connections.



Peripheral Slots

DSU Slots

Peripheral ports

2 Mb Links

1 x Main





1 x Main
1 x Peripheral





1 x Main
1 x Peripheral
½ x DSU





1 x Main
1 x Peripheral
1 x DSU









1 x Main
1 x Peripheral
1½ x DSU





1 x Main
2 x Peripheral





1 x Main
2 x Peripheral
½ x DSU









1 x Main
2 x Peripheral
1 x DSU





1 x Main
3 x Peripheral









1 x Main
3 x Peripheral
½ x DSU





1 x Main
4 x Peripheral






Each Peripheral Cabinet will connect to an SX2000 Light Control Cabinet or SX2000 MICROLIGHT Main Cabinet via fibre optic cable and has 192 interface ports. Each of the 12 interface card slots has 16 ports. Any peripheral card type can be installed at any time in any of the 12 universal card slots. All ports are universally wired to the associated wiring frame as standard.

A Peripheral Cabinet consists of the following components:

  • 12 x Peripheral Interface Card slots;
  • AC Power Converter;
  • Peripheral Switch Controller;
  • Fibre Interface Module (FIM).

SX2000 Peripheral Cabinet

Peripheral Interface Cards

Peripheral Interface card Peripheral Devices supported Circuits per card
ONS Analogue Telephones (25 volt) 16
OPS Analogue long line telephones (50 volt) 8
DDI/LOOP TIE Direct Dial Trunks 4
LS/GS TRUNK Analogue Exchange trunk 8
E&M TRUNK Private Wire 4
AC15 TRUNK Private Wire 8
DNIC Superset Telephones and Datasets 16


Digital Services Cabinet
Digital Services Unit (DSU) Cabinets are connected to an SX2000 LIGHT Control Cabinet or SX2000 MICROLIGHT Main Cabinet via fibre optic cables (2) and can accommodate up to 4 x DSU cards. A single fibre cable connection will support 2 x DSU cards.
A Digital Services Unit (DSU) Cabinet consists of the following:

  • One 200 Watt Power Supply;
  • Peripheral Resource Cards (2);
  • Two Fibre Interface Modules;
  • DSU card(s)
DSU cards

CEPT Formatter

Interface for 2 x 2 Mbit/s links each of which can be individually software configured for DPNSS/APNSS, or DASS 2 (ISDN30). Each link comprises 30 traffic channels, 1 signalling channel and 1 synchronisation channel to CCITT G703 and G734 standards.

Communications Processor card
This is a general purpose processor used for communication between the SX2000 and an external host computer. It will support Host Computer Interface (HCI) applications.

Conference Card
This card will increase conferencing capability to 64 simultaneous users. (24 channels are provided as standard).

DS1 Formatter
This is a digital network interface card provided for specialist or overseas applications only.

Data Transceiver
The data transceiver interprets commands and returns call progress messages to the user of a data terminal or PC.

SX2000 ISDN Server
The ISDN Server is a unit which connects the SX2000 to the existing ISDN network. The ISDN Server behaves like a CEPT Formatter Card, providing digital network control of serial links. All necessary conversion is performed within the ISDN Server, and necessary interfaces are contained within the ISDN Server.

The ISDN Server offers the SX2000 end-to-end connectivity, this means that analogue conversion is not necessary and that digital transmission is extended to the subscriber's premises, enhancing SX2000 services.

The ISDN Server uses Primary Rate Interface (PRI) cables to connect with the ISDN Public Network. The PRI is a combination of channels creating a specific interface between the SX2000 and the Public Network. The PRI consists of 30 x B-Channels, 1 x D-Channel and 1 x Synchronisation/Frame channel. The B-Channels are 64 Kbit/s bearer or traffic channels used to carry voice or data, The D-Channel is a 64 Kbit/s channel used for signalling and user data. The Synchronisation/Frame channel is used to establish and maintain the circuit.

The SX2000 ISDN Server operates as a CEPT Formatter connecting calls in a DPNSS format. ISDN calls are presented to the SX2000 as DPNSS/DASS2 calls. The ISDN Server behaves like a Digital Service Unit (DSU) running Euro-ISDN/DPNSS software and protocols.

The ISDN Server is connected to the SX2000 by coaxial cables and provides digital network control of serial links.

SX2000 Dimensions
SX2000 cabinets are similar in construction to PC towers.

ISDN Server and DSU cabinets are approximately (H x W x D mm) 490 x 230 x 460
LIGHT Main Control, MICROLIGHT Main and Peripheral cabinets are approximately (H x W x D mm) 490 x 460 x 460


Connection to UK PSTN
The SX2000 is fully approved for connection to the PSTN and meets BTR 1050 issue 5. In addition the installation commissioning procedures of the SX2000 and all associated equipment conform to the Health and Safety at Work Act and all relevant British and I.E.E standards as specified by the British Approvals Board for Telecommunications (BABT).

The Approval Numbers are:
NS/1412/123/D/022046 for systems without DDI;
NS/1412/123/F/451637 for systems with DDI.

SX2000 analogue and digital (DASSII and Q.931) interfaces for exchange lines and Direct Dialling In (DDI) exchange lines are approved for connection to the PSTN.

The approval includes AC15a and E & M (SCDC5) analogue private wire interfaces and the digital 2 Megabit DPNSS service (including the low speed option known as APNSS).

The SX2000 hardware is certified as conforming with the required safety standards as defined in BS6301.

Telephone Approval Numbers
Mitel Superset telephones are approved with system.

Any telephone categorised by the Department of Trade and Industry in Lists 1 to 12 incl. may be connected to the SX2000.

Branch Systems General Licence/Network Code Of Practice
Each of the proposed SX2000 system are fully approved under Section 22 of the British Telecommunications Act by the Department of Trade and Industry for connection to the PSTN. However, it is the configuration and operation of the network which must comply with the technical requirements specified by the Network Code of Practice (NCOP), under condition 4 of Branch System General Licence (BSGL).

Key Systems
The SX2000 is an approved host and therefore any approved subsidiary key systems which conforms to BSI 84/63648 can be used on the Mitel PBX.

The SX2000 LIGHT meets the requirements of BS6527 Class B pertaining to Spurious Signals Generated by Data Processing and Electronic Office Equipment.

BS6572 is being renumbered to a European Number - EN55022.

International Standards
The SX2000 conforms to the following international standards.

EIA Interim CIS 4 Jan 82
BTR 1050 Issue 5
BTR 1080
AT & T Pub 48002
EIA Standard RS464
EIA Standard RS470

CCITT G Series Standard
The SX2000 is a digital switch and fully meets the CCITT (Blue Book) G732 2.048 Mbit/sec Digital Transmission System employing A law encoding. The SX-2000 also conforms to the CCITT recommendations G703, G704 and G711 as appertaining to 2Mbit digital transmission.

The SX2000 system proposed conforms to the following CCITT international standards:

G703 - Encoding
G711 - A law Modulation
G712 - Audio Performance
G732 - Frame Structure
G811 – Synchronisation

The system proposed does conform to the CCITT G734 recommendation, which defines the characteristics of synchronous digital Multiplex equipment, operating at 1544 Kbits/second.

This is relevant to markets outside the UK.

Electro Magnetic Compatibility (EMC)
The SX-2000 LIGHT is in compliance with the following standards:

EN50082-1 LEVEL 2

All Mitel SX2000 products comply with the EC Directive - official number 89/336/EEC which relates to Electro Magnetic compatibility. Each item is clearly marked with 'CE' to reveal the product's conformity.

SX-2000 Dimensions
SX-2000 cabinets are similar in construction to PC towers.

ISDN Server and DSU cabinets are approximately (H x W x D mm) 490 x 230 x 460
LIGHT Main Control, MICROLIGHT Main and Peripheral cabinets are approximately (H x W x D mm) 490 x 460 x 460

Link to Console description (PDF)

Sales brochure for SX2000 Light (PDF)

Link to Supersets

For more up to date information - Click here for Mitel Web Site


BACK Home page BT/GPO Telephones Search the Site Glossary of Telecom Terminology Quick Find All Telephone Systems

Last revised: September 24, 2021