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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.
ELECTRONIC PRIVATE AUTOMATIC BRANCH EXCHANGE
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
channeled to the particular needs of a telephony exchange:
- mini reed relays at the cross points of the switching network
- system operation under the guidance of a processor
- modular design
THE REED SWITCH
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 'worst case design' 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.
OPERATOR'S POSITION
 The modern-styled operator's 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 operator's 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 operator's 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 operator's position in the administrative mode enables the operator to perform different administrative procedures.
The operator's position is available in a console version and a floor type version.
Universal operation
The universal operation of the operator's position considerably simplifies the operator's 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 operator's position where each group has an
associated call indication lamp and answering push button. Assisted incoming calls are signalled at all operator's 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 operator's 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 operator's
position.
The standard operator's 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 operator's position. Some of these facilities are:
- call handling on demand; the calling party after having requested an outgoing call waits until the operator has established the connection concerned.
- automatic operator's recall when an extension user does not answer an assisted incoming call within a pre determined time.
- automatic routing to the operator's position of unsuccessful DDI calls.
- break-in an exchange line out of a group of engaged exchange lines.
- external call transfer from one operator to another operator in case, a call has to be handled by a particular operator.
- tax metering.
- blind operation.
Additional features
Apart from the normal handling of calls, the operator is also able to take part in the maintenance of the system.
The operator's 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 operator's 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.
FACILITIES
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
- trunk barring
- full secrecy
- dial and key tone telephones
- regeneration of digit information
- line lock-out
- forced release to public exchange
- instant ringing
- distinctive ringing
- first party release
- exchange line routes
- tie line routes
- overflow of exchange line groups
- direct dialling-in
- universal operators operation
- toll ticketing
- dictation service
- data transparency
- data protection
- traffic measurements
- satellite working
User's facilities
- direct dialling out
- abbreviated dialling
- enquiry call
- call transfer
- break in
- automatic ring back
- automatic call forwarding
- follow-me
- group hunting
- chief-secretary service
- add-on conference
- night service
- hot-line
- paging service
- staff location service
Operator's facilities
- common signalling per line group
- common answering per line
- universal access to all lines and extensions
- service classes extensions
- break in exchange line of engaged group
- automatic supervision of delay times
- unsuccessful DD call transfer
- extension line condition display
- number display - extns, tie and trunk lines
- push button selection
- through connection on demand
- through connection on delay
- holding condition
- series calls
- individual call metering
- operator call metering
- call offering with break in
- camp on busy
- operators recall
- call transfer
- position transfer
- operator to operator call
- blind operation
- administrative procedures
- blind operation
MAN-MACHINE COMMUNICATION
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:
- Operator's position
- Teletypewriter
- MMU panel
- Magnetic tape cartridge unit
Operator's 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:
- changing the service class of an extension
- transferring an extension number
- designating an extension for night service
Teletypewriter
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 operator's 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.
MECHANICAL DESIGN
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:
- a standard rack height of 2000 mm
- an overhead duct (200 mm high) for inter-cabinet and inter-row cabling
- a power distribution to each pair of cabinets
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:
- sufficient room for wiring so that accessibility was not impaired.
- easy inter-change of sub-assemblies.
- well protected power distribution.
- ample equipment ventilation.
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:
- A network unit (NWU) for 128 extensions.
- A peripheral circuit module containing 16 identical PCT's.
- A general module containing different types of PCT's.
- A central control unit module.
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. PWB's are employed for the mounting of all types of components which include:
- minireed relays for the switching network
- low power and high power TTL integrated circuits for logic applications
- MOS-ROM and MOS-RAM memory elements
- discrete components for loop detection. tone receivers and generators. Package density is further increased by the use of double-sided printed wiring boards.
DATA SUMMARY
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
- internal traffic - 2%
- external traffic - 1%
Transmission
nominal impedance - 600 to 800 ohms
frequency band - 300 to 3400 Hz
insertion loss
- between 800 and 1000 Hz - less than 0.5 dB
- between 400 and 3000 Hz - less than 0.75 dB
- between 300 and 3400 Hz - less than 1 dB
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:
- 500 line exchange - nominal 33A
- 1000 line exchange - nominal 60 A
- 3500 line exchange - nominal 175 A
Environment
temperature - -5'C to +45'C
relative humidity - normal: 10% to 75% - extreme: 5% to 95%
dissipation per cabinet - less than 350 W
Cabinet dimensions (inclusive cable duct)
- height 2200 mm
- width 900 mm
- depth 460 mm
Floor pressure
less than 600kg/m sq
Distance between exchange and operator's position
less than 300 metres
Signalling
Signalling from telephone set to EBX 8000:
- impulse signalling
- key-tone signalling (CCITT recommendations)
Signalling between EBX 8000 and public exchange:
- d.c. loop signalling with 10 ips or key-tone
- ALS 70 signalling (interface with PRX)
- in-dialling with impulse signalling and MFC signalling (CCITT Nr. R2)
Signalling between EBX 8000 and other PABX:
- d.c. loop signalling or E/M signalling
- inter-register signalling with 10 ips or MFC (CCITT Nr. R2)
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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