BT Revelation Range
Taken from BT CSI 369 (1996)

Approval number - NS/3864/231R/604892

Due to the introduction of the enhanced BT Revelation Caller Display Services (CDS) and the CDS Upgrade different versions of the system will be encountered in the field.  Systems installed before June 1996 are pre CDS systems.  A CDS upgrade may be installed on these systems. Systems installed after June 1996 are CDS Systems.

BT Revelation is a highly flexible feature rich phone system which can be configured as a key system or PBX or a combination of both.  Four system sizes are available, 1+6, 2+6, 3+9 and 4+12.  Each system size may be expanded to any of the larger sizes using 1+0 and 1+3 expansion boards.

Each extension may be equipped with a BT Revelation System phone or a standard approved telephone.  The System phone provides for full hands free operation and has a 16 character LCD display, prompt keys for use when programming and 16 programmable keys.

Two key features of the system are Fax Detect and DISA (Direct Inward System Access).  Fax Detect allows one programmed exchange line to be used for the receipt of incoming Fax calls.  Incoming voice calls will be recognised by the Fax Detect circuitry as normal incoming calls and will be presented to the system as such.  The same line can be used for outgoing voice calls.  DISA allows incoming callers to directly dial the extension number required.  BT Revelation software is Version L.

Two Optional Modules are available, a V24 Module and a Voice Module.  The V24 Module allows connection to a printer for recording of Call Logging details.  The Voice Module gives voice prompts to incoming callers using DISA (Auto Attendant) and also allows callers to leave brief messages.  These modules are available for all Revelation Systems.

A BT Revelation Door phone is also available and BT may also provide site wiring for a Door strike.  Purchase and fitting of the Door strike unit must be arranged by the customer direct with a local supplier.

The system is compatible with Remote Access (RACE) as supplied.  No additional RACE equipment is required.

Pre-CDS BT Revelation Systems
If a customer with a pre-CDS system which has not been fitted with a CDS Upgrade decides to add a new System phone to their system, ensure that they change the dial card which is fitted in the new System phone (this dial card shows a CDS logo) for the second dial card which is packed with the phone (this dial card shows no logo).  The reason for this is that the pre-programmed keys activated by pre-CDS software are different to those activated by CDS software.

BT Revelation Caller Display Services (CDS)
CDS systems include the following enhancements and feature changes:-

  • Access to the BT Network Caller Display Services (CDS).

  • Courtesy Service.

  • Voice messaging on FAX detect.

  • Manager/Secretary working.

  • The feature code for the Global Pick-Up feature has changed from 8 to 66.

  • The feature codes for the System Speed Dial Numbers have changed from 650-699 to 800-899 (there are now 100 numbers).

  • The alarm call feature has been changed.

  • The pre-programmed keys on System phones have changed: the VOICE CALL key is replaced with a MF TONES KEY.

There is new programming available for the Voice Module:-

  • ring time before activation of the voice module.

  • individual selection of the lines on which the voice module is activated when 35* is dialled.

There are no differences in the core installation of pre-CDS and CDS systems.  Additional installation programming codes are for the CDS and Courtesy Service features.  Details of these codes are found in the installation programming section of the BT Revelation Installation and Maintenance Manual, TPU 2233.

NB: Caller Display Services must be provided on each auxiliary line e.g. 4+12 = 4 CDS lines.

The CDS Launch release of software is Version C.

BT Revelation CDS Upgrade

An upgrade is available for pre-CDS systems.  This will give the system CDS functionality and access to the new features listed above except for Courtesy Service and voice message on FAX Detect.

When an upgrade is fitted and tested, the old EPROM should be disposed of locally. The CDS Upgrade launch release of software is Version C?.

Lake Communications Ltd.




Fully approved. Approval number is NS/3864/231R/604892. The PXML number is BABT/PXML/CRA.0073

The PXML is shipped with each system and the current issue is available from technical libraries.  Up to four power fail telephones may be fitted.  The type of telephone fitted must match the type of exchange line i.e. Loop Disconnect/MF.

A Functional Earth is not normally required except for external signalling purposes, e.g. earth recall to a host PBX.

Installation, Configuration and Commissioning procedures are fully documented in the Installation & Maintenance Manual.

Installation, Commissioning and connection procedures must comply with the requirements of OFTELs Quality Assessment Guide (QAG) No 2, alternatively a PCI is required to be undertaken.

Fax Detect
If the customer asks for this feature to be programmed, it is important to understand the following points.

The Fax detect feature should be programmed on one dedicated exchange line and not on auxiliary working.

It should not be used on lines where a high level of incoming voice calls are expected.

On lines set for Fax detect, Incoming voice callers will hear network ring tone, then between 5 and 10 seconds of silence, then BT Revelation ring tone for a maximum of 30 seconds, then silence.

Only those incoming Fax calls which are preceded by a CNG tone will be recognised by the Fax detect circuitry.

On CDS a voice message is provided to callers on lines programmed for Fax Detect (on 2+6, 3+9 and 4+12 systems).  This feature is not supplied on CDS Upgrades.


BT receives a two year Warranty from the manufacturer on all equipment.  The warranty start date is identified on the Serial Number label on CCUs cards and terminals in the following format:

WXJYY (Week Number/Year, e.g. 16/96 = Week 16 of 1996)

Anti-static precautions should be used when handling cards or working in the CCU.  A connector is provided in the system MDF area for connecting a crocodile clip type anti-static wrist strap.

All available maintenance parts are listed below and all are recommended items for inclusion in Maintenance Kits.  Refurbished item codes begin 76XXXX, new item codes begin with 87XXXX. Items with refurbished item codes may only be used where there is no requirement for replacement with new kit.

PSTN line Idle - Capacitance loop A to B
Seize - Loop
Hold - Loop

Standard wiring is used to connect wall mounted Doorphones.  However, if a Doorphone is to be mounted on a door, a flexible connection is required.  This should be purchased locally.

Older Information


The BT Revelation is a flexible, feature rich analogue telephone system designed to work hand in hand with your business.  It can operate as a key system, with all calls answered by all extensions, as a PBX with all calls answered by an operator or as a combination of the two.

The BT Revelation Central Control Unit comes in four different sizes: one line plus six extensions, two lines plus six extensions, three lines plus nine extensions and four lines plus 12 extensions.  Whichever system you begin with, you can easily expand to the maximum capacity.  Each extension can be equipped with either a system phone or any standard single line device (such as a telephone/fax/modem).

The basic system is connected to analogue MF or LD exchange lines.  There is an optional ISDN2 Access Unit which allows for alternative voice connections to either one or two ISDN2 Basic Rate Access connections. 

The System phone

The Revelation System phone makes it very easy to use and programme the BT Revelation. It has a 16 character LCD display and prompt keys to guide the user step by step through the different features.  It is fully hands free so you can make and receive calls, and use features, without lifting the handset.  It also has 16 programmable keys for quick access to the features you use most often.

Technical Specification

Type of System Hybrid / PBX

Exchange Line
Analogue, Loop Calling Unguarded Clear only.  The system is not through fed.
Exchange Line Max Capacity - 4.
Cleardown time - 100 ms.

System phone or approved single line phone
Internal Speech Paths = 3
Extension Capacity Max = 12
System phone Capacity Max = 12
Approved apparatus capacity Max = 12
Switchboard Operator Extn = 20

Extension Loop resistance
200 Ohms (1.4km) 2 wire phones
100 Ohms (0.7km) 4 wire System phones
336 Ohms (2km) Extension 22 only, if used as an external extension

Extension Cabling
Standard 6 wire
using twisted pair 0.5mm

Extension Numbering Range
20 - 31

Approved phone signalling
MF or LD

Approved phone recall signalling
Timed Break

Call Logger Interface V.24 port
1200 baud, 8 bit, no parity, 1 stop bit

Music on Hold
Dependent on Software levels

System Speed dials
Max 50

Alarm Call
Phone can be set to ring at a given time.

The Door phone
An optional door phone is available.  It can be connected to an extension on the system.

Baby Monitor
The phone can be used as a baby monitor. Simply lift the handset of the phone in the baby's room, dial the relevant code and leave the handsets off the hook.  To listen in, dial the baby monitors extension number from one of two fixed extensions.

Call Back
If a busy extension is reached, this facility will call you back as soon as it becomes free.

Call barring
This allows the restriction of certain calls, for example outgoing international calls.  There are five levels of call barring for each extension and these can be different for both day and night service.

Caller Display Services
An additional facility (software dependant) allows you to see the
phone number of external callers.  The number will be displayed on the LCD of the System phone before you answer.  Systems installed before June 1996 will need a software upgrade.
NB Requires
subscription to BTs Network Services

Call Logging (With V.24 module)
A printer can be connected to the system via a V.24 module.  The printer will record the time and duration of incoming and outgoing calls made on the system.  Details are printed as the calls are completed.

Call Park
External calls can be placed on hold in the system and then retrieved at
any extension..

Call pick up
Extension - you can pick up any call (external or internal) which is
ringing at an extension provided you know the extension number.

Global - you can pick up any external call which is ringing either on a central bell or at an extension.

Call waiting tone
Call waiting tone lets you know of
another incoming call when you are already on the phone.  This feature can be turned on and off manually.

Call transfer
External and internal calls can be transferred from one extension to

Camp on Busy
Callers reaching busy tone when calling an extension, do not replace the
handset and the extension will be rung as soon as it becomes free.

Three way conferences can be initiated between three extensions
or two extensions and one exchange line.

DISA (Direct Inward System Access)
This allows external callers to ring straight through to an extension provided they know the number of that extension.  When the caller phones in on a line programmed for DISA they will hear a tone.  The caller then dials
the extension required.  If the extension is busy or an incorrect extension number is dialled, the call will be presented as an ordinary incoming call.
NB Lines must be programmed for DISA an engineer.

Divert From
If away from a diverted extension, you can divert calls to follow you to another extension.

Divert on busy
Divert calls to another extension if the extension is busy.

Divert on no answer
Diverts calls, if not answered, to another extension.

Divert to
Before leaving your extension, divert all calls to another

Do not Disturb
With Do Not Disturb set, callers will receive a busy tone.  Callers using a System phone will also see "Do not disturb" on their LCD display.

Extension Lock
This prevents unauthorised external calls being made.

An ISDN access unit can be fitted to allow access to ISDN lines.

Last Number Redial
This redials the external number that was most recently dialled.

Night Service
The system can be programmed to automatically switch over to
night service at a certain time.  Night service on or off manually. When the night service is on, the night mode ringing calls of service and voice greeting (if installed) come into operation.

Operator Access
Dial access to the system operator.

External page - if a public address system is connected to the system announcements can be made over the system by
dialling the PAs Extension.

External paging answer - if paged over the PA you can call back the person who paged you provided they have not replaced their handset.

Internal Page - all Systemphones can be paged.

Remote access
This allows engineers to dial into the system to carry out remote programming and fault diagnosis over the phone rather than
come to site.

Speed Dialling
Up to 50 numbers
stored on the system for general use up to 10 personal numbers on each phone.



A BLUE/white 2
B WHITE/blue 5
C ORANGE/white 1
D WHITE/orange 6

V24 Port

2 - 3
3 - 2
8 - 7
7 - 8
5 - 5



Time and Date change

Default system PIN = 111

To reset extension (clear DNDs etc)
Dial 79, from any extension.

To return system to default configuration ( clears all programming - this clears everything - be careful )
From the first extension dial 7651799 (ignore beeping), 1901460


The port is a 9 way V24/RS232C port.

Speed = 1200
Data = 8 bits
Parity = none
Stop bits = 1
Handshake = Xon/Xoff

There must be a CLI board installed.

The wiring for the printer/PC:-
RX - pin 2
TX - pin 3
Ground - pin 5
RTS - pin 7
CTS - pin 8

On some lap tops the plug at the lap top end may need pins 6 and 4 linking (IBM).

From Programming phone:-
Dial 70
Dial pin
Dial admin code 99
Enter the call logging option code:-
0 = cancel the CLI output
1 = print all calls as they are completed
2 = print all calls with the last 2 digits of the outgoing call numbers masked
3 = print outgoing calls only
4 = print only outgoing calls with the last 2 digits masked

The print-out data is presented in an 8 column format:-
Col 1 = I/C or O/G call
Col 2 = Date (D/M/Y)
Col 3 = Start time
Col 4 = Duration of call
Col 5 = Line used
Col 6 = Initiating extension
Col 7 =Terminating extension
Col 8 = Digits entered (O/G calls only - 30 only)


Click here for the Programming and User Guides

Newspaper clipping

The Revelation comes in three sizes, the 2 + 6, the 3 + 9 and the maximum 4 + 12, users can start off with the 2 + 6 and at a later date expand up to the 4 + 12 with the addition of extra cards.

The system supports system dedicated key phones (shown right) and standard telephones as well as other devices such as fax machines and cordless telephones.

This system is easy to use and users can access over 40 system features.

Tallaght based Lake Communications has completed development of a telecoms product, the BT Revelation, as part of a IR15m contract for British Telecom.  The product is a telecommunications system for use by small and medium-sized businesses.

Taken from the IE Professional, July 12, 1995


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Last revised: November 23, 2021