BT 2+8

Introduced in July 1991, this system replaced Ambassador, Escort and Minimaster 3 from BT's portfolio of telephone systems.

PXML No BABT/PXML/PBX. 0079
APPROVAL No S/147013/L/502065

User Guide

Programming Guide

The BT 2+8 is a microprocessor controlled self contained switching system which can be configured on site as a PABX or Keysystem, there are two versions of CCU, Original BT 2+8 and 'Enhanced BT 2+8'. Both systems support up to 2 exchange lines with up to 8 extensions and offer normal modern PBX/Keysystem facilities. The system is 'through fed' on Exchange Line calls hence extension terminals must be configured for MF or LD signalling according to the type of signalling supported by the exchange line / host system.

The 'Enhanced BT 2+8' is externally similar in appearance to the 'Original' CCU but has a redesigned circuit board which offers various additional facilities.

Extension telephones may be any BS 6317 approved telephone with earth recall facility and/or 2+8 Systemphones (in any combination but at least one Systemphone is recommended on original BT 2+8 and required for approval purposes on Enhanced BT 2+8). Systemphones may be used as an Operators Terminal in PBX mode or Key Terminal in Key system mode. Later production Systemphones have improved Handsfree performance and will incorporate a stored number memory protection battery.

A 2+8 systemphone is shown on the right.

2 Exchange lines and 8 extension switch.
2 Intercom paths for internal calls. (LD & MF to Exchange)
Power fail Extn 20 to line 1, Extn 21 to line 2.
Power consumption - 20 watts.

Facilities include:-
- Press recall button or dial 41/42 access to exchange lines.
- LED indication of line/extension status
- Last number redial
- Microphone mute/secrecy button
- On-hook dialling with Handsfree LST operation
- Ringer volume control
- Abbreviated dialling
- Speak (Voice announcement to other systemphones)
- Dual signalling (MF/LD switch on base + soft-switch to MF by pressing
- Divert
- Ringer on/off

Additional/changes to facilities offered by `Enhanced BT 2+8':-
- Exchange line access by dialling digit 9
- Four levels of call barring with customer programmable exceptions
- Music on hold interface
- Extension self test
- Exclusive line changes (for Fax machine use), line 2 will only ring extn 21 but all extensions have access to both lines (I/C & 0/G)
- Recall to host PBX by pressing the recall button and then dialling 'digit 71
- Warn Tone no longer applied on external calls
- Off Premises extension (approval pending for external extensions via the Network)

Many facilities involve the use of a Systemphone

Made by Philips BCS Limited

APPROVAL STATUS
Approved for direct connection to the PSTN (loop disconnect or MF4 signalling) or by working as a subsidiary to a host PBX.

BT 2+8 CCU is intended for installation and use in a normal home or office environment on a dry flat wall, it measures not greater than 550 x 320 x 80mm and weighs no greater than weight 5Kg and should be mounted at a convenient working height. The normal limits are usually considered to be, minimum height, bottom of CCU to the floor 1 metre, and the maximum height to the top of the CCU should not exceed 1.75 metres. The CCU is intended to be mounted with the cover fixing screws at the bottom edge, it should not be mounted upright.

Cooling of the CCU is by natural convection, therefore it should not be installed in a confined space and it must have a minimum clearance of 100 mm on all sides with sufficient space to access cover fixing screws.

The CCU should not be sited where it may be subjected to excessive levels of heat, dust, damp or high humidity. Locations near sources of electromagnetic radiation such as heavy electrical switch gear (e.g. lift machinery or electric arc welders) should be specifically avoided.

A Mains plug and 240 Volt, 13 Amp, 50 Hz mains power socket within 2.5 metres of CCU dedicated to the system will be required. A mains conditioning unit (MCU) should not be necessary as the CCU incorporates a mains filter.

A 1.5mm sq. functional earth will need to be provided if:-
(a) The system is subsidiary connected to a host system that requires Earth Loop Recall.

(b) There is a risk of high voltage line surges.
If a functional earth is provided for (a) or (b) above it may be used for Electro Static Precautions.

There is no provision for standby power, Lines 1 & 2 will automatically switch through to extensions 20 & 21, respectively under power fail conditions.

CCU to extension cabling limits (using cable 2503) are:-
25 ohms (approx. 150 metres cabling) for a Systemphone on Original or Enhanced BT 2+8 CCU.
50 ohms (approx. 300 metres cabling) for a standard BS 6317 telephone on Original or Enhanced BT 2+8 CCU (3 wire extension).
336 ohms (approx. 2Km cabling) for a standard BS 6317 telephone on Enhanced BT 2+8 CCU (2 wire extension).

Each (internal) extension (regardless of Systemphone or type of telephone used) must be (6-wire) cabled between the extension terminal strips in the CCU and Master Line Jack at extensions, all 6 conductors must be terminated at Master Line Jacks as per standard wiring practice.

Although earth recall telephones are specified, the earth recall lead (LJU 4) must be terminated on the extension terminal strip in the CCU and not to earth, only the spare (orange/White) conductor is not used and must be insulated and left spare in the CCU.
Multipair cables (equivalent to cable 2503) can be used for extension cabling provided each extension is connected up by with 3 (twisted) pairs. Pairs must not be split.

The extension ports have an output REN of 4 and Extension Bells / Tone callers can be hardwired connected to LJU terminals 3 and 5, and additional telephones via parallel connected secondary LJU's (but only one Systemphone per extension).

SAFETY
The Enhanced BT 2+8 CCU contains a Lithium battery which must not be short circuited as this may cause the battery to burst or leak, also a heat sink which can remain uncomfortably hot for a few minutes after power is switched off.

INSTALLATION
The mains lead is part of the BT 2+8 Power Supply Unit (PSU) and must not be shortened (unless necessary for re-terminating the mains plug). Any excess mains lead should be neatly coiled away, if the mains lead is shortened, it may invalidate the manufacturers system warranty.

The `Enhanced BT 2+8' is supplied with metal cover fixing screws. These are intended for permanent use and are not to be replaced by the plastic screws used on original BT 2+8 covers.

Extensions 20 & 21 will not initialise and `Line busy' LED(S) will be lit on Systemphones unless the exchange line(s) are connected (or on single line systems, the appropriate SW1 switch is operated).

LJU wiring

Only 5 wires are connected at the CCU end

Power Fail wiring

MUSIC ON HOLD
Centre and either outer IDC.

To prevent crosstalk and interference the pairs should not be split and the spare wire of the cable pair should not be used.

The REN of each extension port is 4, but only one Systemphone per extension.

The intercom current feed is in the range 22mA - 28 mA.

External extensions should use extension 27 in preference as this port has extra protection against high voltage surges. Any extension port can be used for an external extension if suitable protection is provided. It is also permissible for signalling converters to be used.

You will lose the hold and recall facilities on 2-wire external extensions. This will mean that once a call has been put through there will be no way to hold or transfer the call.

MAINTENANCE
For safety reasons the CCU must be disconnected from the power supply whenever the CCU cover is removed. Altering the facility switches will have no effect until power is switched off and on again as the switch settings are only read by the system microprocessor when powering up. Any customer programmed facilities, including memory numbers stored in systemphones will be reset when the power is disconnected.

The Enhanced BT 2+8 contains an on board Lithium battery to preserve customer programmed call barring details, diverts, night service or bell-off programming. This battery must be switched on during installation and has approx. 10 year in service life (provided system is kept powered up).

WARRANTY
New units for initial supply or for use as maintenance spares carry a 24 month warranty from the date of manufacture as shown by the first 4 digits (YY WW) of the 11 digit serial number marked on the back of the unit.

The Lithium Battery in Enhanced BT 2+8 CCU should be switched off on any CCU being recovered, stored or disconnected from mains power for any length of time.

PARTS
Description                                                 BT Item code
BT 2+8 CCU complete                                         870446
BT 2+8 Systemphone                                          870447
Enhanced BT 2+8 CCU complete                                870512
BT 2+8 Systemphone (with improved Handsfree)                870513
Wall Bracket (for Systemphones) Clear                       870548
Fuse 72/1 (Antisurge)                                       313873
Fuse 88A/3 (Mains Plug Top)                                 314555

PARTS LIST

LINE TESTING
Capacitor-loop test conditions apply (value of capacitance may test less than a normal DEL terminated by NTES).

ADDITIONAL INFORMATION
(a) Extension telephones - Not all modern telephones with an earth recall button will work on Original or Enhanced BT 2+8.

(b) BT 2+8 monitors the exchange line voltage to determine if the line is free, the line voltage links should be set to '50 Volts or 24 Volts depending on the normal `line idle' voltage. `Line Busy' problems may arise on systems where the line voltage can fluctuate between both of these values e.g. Gfeller Local Line Concentrators (where line free condition may be 20 or 50 Volts) or with WB 1400 systems where the line charged battery can reduce line voltage on long lines, these may be resolved by setting the links in the 24 Volt position.
N.B. the links have been repositioned on Enhanced BT 2+8 but are still supplied in the 50 Volt setting.

(c) Systemphones should not be plugged into the back of add-on units (e.g. Wren or Kingfisher II) where Line Cord conductors 1&6 are interrupted, a 6 way plug-in doubler may be used instead to connect the unit.

(d) Incoming line polarity is important when Original BT 2+8 is connected to the extensions of an Earth recall PBX, the incoming line (A & B wires) may need to be reversed to prevent call drop out when trying to recall the host PBX with certain types of extension telephone (this problem has been overcome on Enhanced BT 2+8).

(e) In the event of mains power failure/disconnection any programmed facilities will be lost on original BT 2+8 CCUs .

(f) Systemphones require approx. 15 - 60 seconds to power-up and handset must be lifted and replaced to initialise the handsfree facility before first use, stored numbers will be lost on mains power failure (later models will incorporate a memory protection battery).

(g) Systemphones may automatically switch to handsfree due to RFI (overcome on Enhanced BT 2+8).

(h) The bells of any telephones (or extension bells) connected to the same extension as a Systemphone may tinkle whilst Systemphone dials out (overcome on later systemphones).

(i) The extension self test facility on Enhanced BT 2+8 is intended to be used as a confidence test to avoid unnecessary change outs where a fault complaint cannot be reproduced, as it involves changing the Pulse/Tone signalling switch position on Systemphones, the test should be used with caution.

Last revised: March 03, 2006

FM