APPROVAL No. NS/1208/23/D/021737/C

Line Interface Module (LIM), group switch, TJF, Teleprinter (Texas Instruments 765 or 703), Deck mounted tape deck(s) (Tanberg TDC3000/IR), Harmer and Simmons power plant type varies in accordance with size of system.

Made, distributed and installed by:
Ericsson Telecommunications Ltd (ETL)
Viking House, Foundry Lane, Horsham, West Sussex
Telephone 01403 64166.

Approved for private supply and installation in July 83.

This range of telephones is known by Ericsson as the 'DBC' family of digital telephones. There are four telephones in the same basic design, with modular construction and the same general functional specification. The main differences between them is the features and programmable keys found on each model. The Dialog 2501 is the standard digital set, the 2531 is the intermediate model and the 2561 is the top of the range. The 2563 is almost the same as the 2561 but has more programmable keys.

The 2501 has two line access keys and five programmable function keys, one of which has an associated LED. It is also equipped with a Transfer key, a handset volume control and a volume control for the ringer.

For voice/data applications, the 2501 can be used with the TAU-PC.

The 2531 has all that the 2501 has, plus an inquiry key (which acts as a third access to the 'own' line), 12 programmable keys with LEDS, a built in speaker (monitor only) and a ring pitch control. It also has Mute, Programming and Speaker keys.

For voice/data applications, the 2531 can also be used with the TAU-PC.

The 2561 is the top of the range in this family. It has everything that the 2531 has, plus completely hands-free operation and a built-in liquid crystal display which provides calling/called number display and a variety of other useful information.

The 2561, like the others, can be used in conjunction with the TAU-PC to provide simultaneous voice/data communications.

The 2563 is similar to the 2561 but has 43 keys.

These telephones are fully supported on R4 and later releases of software. They may be configured by using the guidelines that are detailed in section 7, Key Layout and Commands in conjunction with the Ericsson site documentation.

2. PRE R4 S/W
If these telephones are to be configured on pre R4 software then certain adjustments need to be made to the software for successful operation. These adjustments can only be undertaken by BTFSU (BC/CSP/BCC535) or Ericsson Ltd. There may also be slight differences in the ITYPE commands, BTFSU will be able to advise.


Ericsson's MD110 business communication systems deliver a new architecture to support new ways of working for an increasingly mobile work force. The MD110 is the world's most advanced PBX system, offering powerful solutions for today's and tomorrow's networks. This unique system combines Ericsson's world-leading expertise in switching, networks and mobile communications to deliver the benefits that users demand.

Based on a modular and distributed architecture, the MD110 provides the foundation for a unified network that supports integrated voice, data and multimedia applications. Because of its distributed architecture, the MD110 provides a high degree of fault tolerance and excellent scalability, from a few hundred to 35,000 or more users in an office, campus or enterprise environment. Full mobility is supported in any configuration and across multiple locations.

Ericsson's MD110 stands out as an exceptional system that prepares you for the future while providing a cost-efficient solution for today's business communication needs. Whatever your requirements, today or tomorrow, there is an MD110 system that will exceed your expectations. Today, there are more than 12 million business users who reply on the MD110 and who have placed their confidence in Ericsson to protect their investment in the future through continuous system enhancements.

A PBX is no longer a standalone system for voice communications. Today's business need a unified network for both voice and data is an integrated part of a larger communications infrastructure. The MD110 is unique in providing a truly open platform that supports all major existing and emerging standards and powerful network management functions to provide the ultimate in flexibility in supporting the flow of all types of information into and out of our organization.

System structure and configuration

Distributed architecture
The distributed architecture of the MD110 PBX is based on the three main principles:

Distributed control system

Each stack is controlled by its own processor and switch, providing outstanding redundancy.

MD110 feature Link:

  • 100% feature transparency

  • scalable capacity from 2 to 16 Mbit/s
  • control systems can be connected by fibre, microwave, coax or copper

Software blocks

  • Regional software for autonomous control, handling and provision of functionality for all users served by the stack.
  • Central software only for inter-module processing. To ensure high reliability and fault tolerance, this software is always loaded in several PSMs simultaneously.

The modular system is stackable using the building-block principle. The system can be configured and enhanced according to customer requirements. The system is designed to achieve maximum customer freedom and flexibility, according to the following principles:

  • Buy only what is needed today.
  • Extend the system when the need arises.
  • Choose the modules with the functions actually needed.
  • Structure the system according to available space. Modules may be stacked or spread out.

The MD110’s modular design and distributed processing power (massive multi-processing) make it unique among business communications systems.

Customer benefits
These key design principles and the modular system structure gives the MD110 its unique benchmarks and provide customers with benefits in terms of:

  • Scalability
  • Flexibility
  • Reliability and availability
  • Decentralization

MD110 PBX distributed architecture provides flexible processor power, allowing you to dimension traffic handling capacity and system size to exactly match your requirements. In centralized processor systems you either have too little or too much.

Stacks may be built with one to four stackable modules. Stacks may be placed side-by-side or back-to-back.

The Processor Switch Module (PSM) uses its own control system and switch and works as an autonomous system or as integrated part of a larger system. One PSM can have up to 3 interface modules (IFM) and then support up to 640 extensions (traffic and configurations depending). Larger systems are built by simply adding processing and switching capacity (PSMs and IFMs) as the system grows. In this way, integrated systems with more than 20.000 extensions and full feature transparency can be built.

Flexibility (even processor load)
With distributed processing and switching there is always enough processing and switching power in the system to provide the required performance to end users in optimum manner, independent of system size. Investing in a new system does not have to be expensive. Extra processing and switching power are added as the organization grows.

The use of universal hardware and software in the MD110 makes reconfiguration and expansion of the system easier and less expensive.

Reliability and availability
Since full processing and switching power is distributed to all PSMs a fault in hardware or software affects services only within the malfunctioning PSM, not the entire system.

In addition, each PSM is capable of autonomous operation if the feature link to the rest of the system fails.

The MD110 software is divided into central and regional operating segments. Each PSM contains all the necessary regional software to ensure complete control of intra-PSM call processing.

Communication between PSMs in controlled by central software, which is accessed as required by the originating PSM. The central software is duplicated in several PSMs for added reliability.

Decentralized system on the premises or campus.
The modules can be flexibly distributed over a campus area or within the office keeping 100% feature transparency.

The modular structure of the MD110 system in combination with the unique advantages of distributed processing enable Ericsson to supply systems precisely tailored to customer requirements and the physical layout of their organizations.

The MD110 PBX has no predefined system configuration. Instead, users can build up an integrated voice and data network using standardized elements (modules). Processing power (PSMs) and capacity (PSM/IFM) can be loaded where they are needed, to suit users’ unique communication requirements.

Interconnection of modules (PSM/IFM) is achieved using the unique MD110 PBX feature link, providing 100% feature transparency, independent of distance between the modules and number of user.

System enhancements
In addition to the distributed system architecture and modular building practice, the latest MD110 PBX system delivers significant new functionality:

  • Cordless mobility
  • Networking
  • Open interface
  • Call center
  • SNMP network Management
  • Integrated voice mail
  • Personal numbers

Cordless mobility
The MD110 provides the market’s first cordless PBX. Ericsson is showing its leadership in mobility by fully integrated DECT (digital enhanced cordless telephony) functionality with the business communication system. This integration takes full advantage of the distributed MD110 architecture and supports up to 20.000 cordless users in one system.

Users are thus mobile anywhere in the coverage area, which may include multiple sites. Integrated roaming and seamless handover are supported as optional software in the MD110. No additional server is needed. With the personal number service, mobility is further enhanced, letting users respond to business calls wherever they are.

The MD110 PBX system is designed from the ground up to provide the foundation for a unified network that supports integrated voice, data and multimedia applications. Feature transparency throughout the network and across multiple sites for all voice, data and multimedia services has always been a defining feature of the MD110 PBX system.

Now, the system has been enhanced with Dynamic Route Allocation (DRA) to support feature transparency over public switched ISDN or IDN networks for PBX interconnects, thus eliminating the need for expensive dedicated leased lines. DRA uses voice compression to support up to four calls on one channel, resulting in substantial savings on traffic costs.

In addition to enhancing cost-efficiency for existing network solutions, the new DRA functions allow full network integration of corporate sites without dedicated trunks and provide an easy upgrade path to tomorrow’s ATM networks.

Open Interface
The MD110 PBX system is based on standards and open interfaces that easily add new capacity, functionality and technology when you want, supports a number of multimedia accessories and software options that enable personal data and video conferencing. There is a cost-effective and state-of-the -art narrowband solution delivered directly from the MD110 PBX system via a standard ISDN S0 interface. For customers with more stringent quality requirements, there is also a broadband solution based on isochronous Ethernet. In both cases, MD110 multimedia services and applications are based on open interfaces and designed to allow easy integration of third-party hardware and software.

Call Centre
The MD110 PBX system with Automatic Call Distribution (ACD) software, provides and ideal platform for large organization that handle hundreds or thousands of calls daily.

This function not only route incoming calls to the correct person and department but also organizes extensions into call groups, which may be in the same office or in different locations. Depending on your requirements, various options are available for call group supervisors and agents, including Call Centre Manager and Agent Desktop applications.

The MD110’s already superb network management functions have also been improved. A standardized management system for the entire network is being introduced, which is based on the industry-standard SNMP (Single network management protocol) using TCP/IP and PPP (over the LAN or via modem).

New SNMP tools are being added to the Dynamic Network Administration family of network management tools, which includes Directory Manager, Extension Manager, Performance Manager, Node Manager and Event Manager, as well as the Management Repository Server, which is common to all applications, and Operator workstation and Personal screen Call applications for users.

Personal Number
Personal Number for mobile communications combines different access methods (wired extensions, business cordless, cellular, PSTN and pager) with a new generation of personal services to help mobile users manage their calls.

The personal Number service will keep track of where to locate the user. Each user may have up to five personal profiles, which may be activated according to the situation (in the office, traveling, at home, etc.). the profile determines what happens to incoming calls, which will be forwarded to different telephones in a pre-defined order or transferred to a back-up service.

Integrated Voice Mail
The MD110 PBX supports voice mail on a card as a system option

Each card supports up to 300 mailboxes and 16 simultaneous sessions.

Up to 10 hours of voice mail messages can be stored on a separate hard disk. Basic functionality includes storing, scrolling retrieving and deleting of messages. Users may record personal greetings.

Incoming calls to the correct person and department also organizes extensions into call groups, which may be in the same office or in different locations. Depending on your requirements, various options are available for call group supervisors and agents, including call centre manager and agent desktop applications.

Click here for MD110 tones


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Last revised: November 09, 2020