Supplied by Pye/TMC the EBX8000 was a SPC reed switched telephone system with an ultimate capacity of 8000 extensions.

Introduced in the late 1970's.

EBX 8000

The EBX 8000 is a stored program controlled reed exchange capable of continuous expansion from 250 to 8000 lines, and designed for standard traffic capacities of 0.12, 0.16 and 0.24 Erlang per extension.

The benefits of the system as outlined on these two pages are mainly derived from the use of three modern developments which have been channelled to the particular needs of a telephony exchange:

The mini reed relays employed by the EBX 8000 at the crosspoints of the switching network were specially designed for telephony applications.

When energized, these relays switch the paths through the network. The reed contacts are able to carry loop-current, microphone current and ringing current, and they also provide excellent isolation between the switching network and the central control, resulting in a symmetrical network.

Altogether, the low level of switching noise, minimal contact resistance and small dimensions of the reed switch make them ideal for use in the switching network. And, apart from switching speech paths, the reed contacts are fully compatible for data transmission. The reed contacts are hermetically sealed in a glass capsule filled with inert gas which affords a very high degree of protection against environmental conditions of temperature, humidity and dust. Ruthenium alloy contacts are used, which have a multi-million operation capability, a fast operating time and utmost reliability. Furthermore, the small size of the reed switches make them ideally suited for building up switching matrices on a standard printed wiring board.

Fast, simple installation
All aspects of the system have been modularised where possible; right from the standard-sized cabinets to the incremental memory modules. This has made it possible for all cabinets to be delivered pre-wired, factory tested and fully-assembled, leaving the minimum of cabling to be completed on-site. Installation is further eased by the use of plug-in connectors for printed wiring boards and cable joints. In fact, compared to conventional exchanges, installation time per line is more than halved.

Flexible and future-conscious
The extensive use of software controlled functions makes the exchange flexible. Different facilities and operating procedures are easy to implement. As well as being convenient, this results in obvious economies of manufacture and system administration. Furthermore, modifications and new facilities can be introduced at some

time in the future with similar ease. In the coming years, telephone networks will increasingly be used for transmitting data. This trend poses no problems for EBX 8000 users as the minireed contacts are fully compatible with the needs of this form of communication too. In fact the data transparency requirement was one of the reasons why minireed contacts were chosen as crosspoints of the switching network.

Silent operation
The use of minireed relays and computerised control together with the absence of any forced cooling equipment means the EBX 8000 operates noiselessly.

Space saving
With stored program control, many telephony functions previously performed electro-mechanically are taken over by software. This, together with the high packing densities made possible by miniaturisation techniques have resulted in a considerable reduction in the floor space requirements of an EBX 8000 compared to even the most modern electro-mechanical system. In these days of ever-increasing building costs, this space saving feature is an important advantage.

Utmost reliability
Top quality components employed in the Ďworst case designí situations are used throughout the EBX 8000. And, hermetically-sealed minireed contacts at the heart of the exchange - the modular switching network - are noted for their reliability even under adverse operating conditions of dust, humidity and temperature variations. Further built-in safeguards include a specially structured set of system programs and a duplicated central

control unit. By having the two central control units operating in synchronism, it is possible to switch automatically from one to the other without loss of performance. Thus, even when the inevitable faults do occur, the operation of the exchange remains uninterrupted.

Continuously expandable
In conventional systems, increasing the number of extensions can be difficult and often involves a great deal of structural alteration. There are no such problems with the EBX 8000.

It is possible to expand right up to 8000 lines with ease. This results from the use of pre-wired cabinets, pre-fabricated cabling and plug-in units.

High quality transmission
The use of minireed contacts guarantee a very low level of switching noise. Transmission of both speech and data through the switching network of the EBX 8000 is thus of an extremely high quality.

Low power consumption The combination of a very efficient central control and minireed relays means that the EBX 8000 needs considerably less power than other exchanges of this nature. This is an advantage in itself, but it also leads to others as natural air convection is sufficient for cooling purposes and

expensive, bulky cooling units are not required.

Easy to service Fault detection units and self-checking, software-controlled routines are continuously in operation. The malfunction of any part of the system is thus immediately detected by the processor and the system is automatically reconfigured so that performance is not affected.

The fault condition is signalled, allowing the operator to begin the standard fault rectification procedures. In almost all cases, the final procedure involves nothing more than the replacement of a module such as a printed wiring board.

The modern-styled operatorís position has been designed to fit every office or reception environment. The operators are responsible for a considerable part of the service rendered to the extension users and the external subscribers.

To this end, standard ergonomics in combination with the experience obtained from a large number of operators, have been compiled in the design of the operatorís position.

All the various lamps and push buttons have been grouped in separate functional fields. Buttons commonly used are placed in the most accessible positions and whenever possible lamp/ push button combinations are used.

The display field of the operatorís position informs the operator about the condition during call handling. The text of the display field can be indicated in different languages.

Apart from call handling the operator is able to take part in the system maintenance. Placing the operatorís position in the administrative mode enables the operator to perform different administrative procedures.

The operatorís position is available in a console version and a floor type version.

Universal operation
The universal operation of the operatorís position considerably simplifies the operatorís task and keeps the number of lamps and push buttons to a minimum.

Groups of exchange lines, tie lines and recording lines are connected to each operatorís position where each group has an associated call indication lamp and answering push button. Assisted incoming calls are signalled at all operatorís positions and handled in their order of arrival when queues are formed.

Various conditions are similar for all groups of exchange lines, tie lines and recording lines alike. This has made it possible to have just one lamp and/or push button on the operatorís position for such a condition. For example, the E push button is used to terminate the assistance of any call handling.

Individual calls like series calls, holding condition and tax metered calls are handled at the associated operatorís position.

The standard operatorís position has 6 incoming and 6 outgoing exchange/ tie line group and can easily be modified to incorporate an increased number of groups.

In fact 18 incoming and outgoing exchange/tie line groups can be provided.

In cases where there are bothway exchange/tie lines an incoming and an outgoing exchange/tie line group are combined to form a bothway group.

Apart from the provisions for normal call handling like series calls, holding condition, break-in and camp-on busy, a number of additional facilities has been incorporated in the operatorís position. Some of these facilities are:

Additional features
Apart from the normal handling of calls, the operator is also able to take part in the maintenance of the system.

The operatorís position can be placed in the administrative mode enabling the operator to change various system parameters whilst traffic monitoring continues as normal.

Using the keypad push buttons and the number display, the operator can change these parameters by executing administrative procedures. Different procedures are available in order to change extension service class, transfer extension number, designate night extension, designate chief-secretary combination, and others.

Supervisory facilities are provided by different lamps for indicating alarm conditions. An alarm thus enables the operator to immediately see the urgency of a fault. The type of fault can be displayed which enables the operator to give precise instructions to the service engineer to effect a very rapid repair.

Display field
The display field of the operatorís position provides the operator with an immediate picture of call handling conditions.

The two four-digit displays are used to indicate an extension number, an exchange/tie line number or metering pulses.

The other displays indicate conditions like ringing, busy, answered, internal cleared, external cleared, number unobtainable, major alarm and minor alarm.

The EBX 8000 exchange offers a large variety of facilities to the extension users and operators.

Moreover the exchange is provided with facilities which contribute to the efficiency and technological superiority of the system.

System facilities

Userís facilities

Operatorís facilities

Maintenance of the EBX 8000 system is effected through man-machine communication whereby certain utility equipment works in conjunction with the operational maintenance programs. Administrative and maintenance personnel have the following utility equipment at their disposal:

Operatorís position
When an operators position is switched to the administrative mode, the operator is able to pass on instructions to, and receive replies from the system whilst traffic monitoring continues as normal. The keypad is used as an input device and the display panel as an output device. Typical administrative procedures performed by this means are:

A teletypewriter can be connected to the system and then be used to produce a report or initiate a conversation, that is executed in the form of a simple dialogue. Requests are forwarded via the key board and the associated answers are given via the printer.

MMU Panel
The man-machine unit (MMU) panel is an intermediate device between the system and those who want to communicate with it.

Various lamps and switches on the MMU panel are available for the administrative procedures. The lock switch on this panel can be used to select different pre-set procedures, thus ensuring the correct procedure is initiated for a particular application.

The alarm conditions indicated at the MMU panel correspond with those at the operatorís positions. In case of a fault the service engineer will start a procedure to read a fault report, indicating the nature of the fault. After this fault has been rectified, the engineer will start a recovery procedure.

The loading of the stores of the processor is initiated from the MMU panel in conjunction with the magnetic tape cartridge forwarding data from the load tape to the system.

Communication with the system, effected via the magnetic tape cartridge is controlled and supervised by the MMU panel.

Magnetic tape cartridge unit
This input and output device is used when large amounts of data need to be transferred to or from the system.


The attention given to the mechanical design aspects of the EBX 8000 has been just as Thorough as that applied to the electronics. It has resulted in a cabinet construction with the following features:

High packing densities achieved through the use of miniaturisation techniques were taken into account when designing the cabinets and special steps were taken to ensure:

Standard construction All cabinets of the EBX 8000 system are similar in construction, consisting of two standard racks with added front doors. They can be placed against a wall, back-to-back or free-standing and have an overall height of 2200 mm (including cable duct) a width of 900 mm and a depth of 460 mm.

Each rack can contain six shelves. Modules of standard 1, 2 or 3 shelf sizes can be directly fitted into the rack.

Typical modules are:

Printed wiring boards are installed with similar ease as up to 30 boards can be slotted into a shelf.

Cabling and wiring Cabling, inter-shelf and inter-module wiring are all prepared at the factory. Top quality cabling is manufactured at the correct lengths and supplied complete with connectors which are subsequently plugged into prepared locations on the shelves, and the wiring is assembled using the latest wire-wrapping techniques to ensure highly reliable connections. This quality approach to design is continued with the printed wiring board connectors which utilise phosphor-bronze connector springs coated with rolled gold to impart high mechanical reliability and low contact resistance.

Printed wiring boards
After careful consideration, a standard printed wiring board size of 280 x 236 mm was chosen for use throughout the EBX 8000 system. PWBís are employed for the mounting of all types of components which include:


System type
stored program controlled reed exchange 

Capacity range
250 to 8000 extensions

Traffic capacity
standard 0.12, 0.16 and 0.24 F/ext.

Grade of service

nominal impedance - 600 to 800 ohms
frequency band - 300 to 3400 Hz
insertion loss

Loop resistance
including telephone set: less than 1600 ohms

Leakage impedance of speech wires
more than 20 k ohms

Power supply
voltage - battery - nominal -48 V

busy hour current:

temperature - -5įC to +45įC
relative humidity - normal: 10% to 75% - extreme: 5% to 95%
dissipation per cabinet - less than 350 W

Cabinet dimensions (inclusive cable duct)

Floor pressure
less than 600kg/m sq

Distance between exchange and operatorís position
less than 300 metres


Signalling from telephone set to EBX 8000:

Signalling between EBX 8000 and public exchange:

Signalling between EBX 8000 and other PABX:

The EBX can be used to form networks applying one of the above mentioned signalling methods. Furthermore, two and four wire switching can be executed in the exchange.

Taken from the Philips EBX8000 sales brochure


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Last revised: January 30, 2021