PXML No. 3
Approval No. BABT/PXML/3 DBS0014

Programming guide

The Navigator is a microprocessor controlled Key and Lamp Unit available in either 8+8 or 16+16 capacities. The central unit is wall-mounted and contains the power unit, processor, interfaces, line filters and IDC terminating boards for exchange and terminal wiring. A central unit supplied as an 8+8 system can be expanded to a 16+16 system by fitting additional interfaces, line filter, expansion and IDC terminating boards. When an 8+8 system is expanded in this manner, all the existing terminals will normally require replacing with 16+16 terminals.

The system supports Call hold, Call transfer, Conference and is programmable by the customer.

Note: Terminals are interchangeable, but an 8+8 terminal fitted on a 16+16 system will only be able to access the first 8 lines and terminals.

8+8 Terminal 16+16 Terminal

From the 17 August 1990, Navigator will be supplied with new software, Version V4.2 offering the customer four additional features:-
- Answer Longest Waiting Call
- Conference Calls
- Ringing Detect Interval
- Timed Break Recall Interval programmable between 77.7mS up to 1,243mS.

A mains filter is included within the CCU to provide protection against mains borne interference, a separate mains filter should therefore not be necessary under normal operating conditions.

Cabling of LJU's is carried out using cable equipment 6 wire 2503F which is terminated on a LJU 2/3C or 3/3C. Navigator terminals either 8+8 or 16+16 are plugged into the LJU's, the associated telephones (approved for connection to the Navigator system) being plugged into the rear of the terminals.
Signalling can be either Loop Disconnect or MF which is determined by the associated telephone. Recall from the CCU to the parent exchange can be either Earth-Loop or Timed Break, programmed from terminal 1, default is Earth-Loop. Detection of incoming ringing can be either Short (Auto Exch) or Long (Manual Exch), programmed from terminal 1, default is Short.

Made by GEC Ltd

Approved for direct connection to the PSTN (loop disconnect or MF signalling) or by working as a (List A or D) subsidiary system (loop disconnect or MF signalling) connected to a (List C) PBX.

The system is approved to provide either Earth Loop or Timed Break Recall.

Approved software levels for Navigator are:-

System Software   V 1.18  or        (IC 16 on main processor)
                             V 1.20  or
                             V 1.22  or
                             V 4.1   or
                             V 4.2   or later

Terminal Controller V 15.1  or later   (IC 7 on main processor & expansion board)
The system has a nominal power consumption of 80 watts.

There is no provision for standby power.  In the event of a power failure each exchange line is connected to one extension, line 1 is connected to extension 1, line 2 to extension 2, etc.

In the event of a system having more exchange lines than extensions, those exchange lines which do not have a corresponding extension cannot be accessed during power fail.

New units, either those supplied with the system or as maintenance spares, carry a 24 month warranty from the date of manufacture, shown as year and week on the self-adhesive label fixed to each circuit board.


GEC ITEM CODE          DESCRIPTION                  BT ITEM CODE
D143040/A              8 WAY CCU                   	870265
D143040/B              16 WAY CCU                  	870305
DPA1584/A              MAIN PROCESSOR BOARD        	870317
DPA1585/A              EXPANSION BOARD             	870267
DPA1583/A              LINE INTERFACE BRD      		870307
DPA1599/A              LINE FILTER BOARD            	870306
DPA1516/A              TERMINATION FIELD BOARD 		870266
D143044                POWER SUPPLY UNIT             	870318
D143631                MAINS FILTER
D143026/ADA            8 WAY TERMINAL           	870268
D143023/ADA            16 WAY TERMINAL             	870269
                       RIBBON CABLE 1A             	870324
                       RIBBON CABLE 2A            	870325
Mains input (Time Lag) 72/3/15                          314217
FS1 & 2                   73/1                          314179
FS3                       73/4                          314004
FS4                       73/3.15                       314024
FS5                       73/0.2                    	665468

Auto Answer Facility    If using a headset, extensions specified by the user can be programmed to automatically answer an incoming call after a certain amount of rings, without having to press any buttons
Buzzer Volume The volume of the ring tone can be altered to suit individual requirements
Call Hold Calls can be held so that the user can answer another incoming call or make enquiries to other extensions
Call Transfer Calls answered at one extension can be transferred to another
Conference Calls Two extensions can speak to the same incoming caller
Exchange Lines Every exchange line has its own LED and button
Extensions Every extension has its own LED and button
Powerfail The system allows the answering of incoming calls in the event of a power cut

Note: Every Key and Lamp unit requires a standard telephone plugged into it.

If the original 8 x 8 system was installed with 8 x 8 NAVIGATOR terminals it will be necessary to replace them with the 16 x 16 terminal.

To test the NAVIGATOR system follow the points listed below:-
To expand it will be necessary to add the following hardware to the existing 8 x 8 CCU.   It will also be necessary to remove the radio frequency interference box lid to fit the PCB's.

1   Expansion Board   870267
1   8 Way Termination Board   810266
1   Line Filter Board   870306
4   Line interface Boards   870307
Ribbon Cable 1A   870324
Ribbon Cable 2A   870325


Only line jack units -/3c are used with a maximum distance of 300 metres (using 0.5mm cable).  A functional earth is also fitted using 1.5mm cable.
The mains is fused at 3 amps.
System power consumption is 100 watts.

1   G/W   1
2   B/W   2
3   O/W   3
4   W/O   4
5   W/B   5
6   W/G   6

4 5
3 6
2 1

Idle - Normal capacitance loop.
Seized - 220 ohms at 39 ma. This is an active termination and will measure different resistance values at all other currents.

a. Navigator CCU has a Ringer Equivalence Number (REN) of 3.

b. Signalling limit CCU to Terminal. 50 ohms loop of a single pair i.e. about 300 metres distance when using 0.5 mm cable.

c. Traffic carrying capacity. Non blocking system.

d. Transmission loss through CCU is zero dB.

e. Recall Signal Duration. (Timed Break 77.7mS [default] & Earth Loop 440mS).

f. It must be noted that any wiring connection error to the Line Termination Boards or the Line Jack Units can result in permanent damage within the CCU, terminals or both. Check all the extension line connections before switching on the mains supply.

If block wiring or multiple cables are used for terminal distribution, a detailed record should be left with the system identifying wiring connections.

Exchange line connections are not polarity sensitive.

g. A rechargeable Nickel Cadmium battery provides power to maintain the programmable options during a mains fail situation. The battery is normally trickle-charged and has a capacity to maintain the memory for up to 4 weeks.
The battery service life should be in excess of 5 years.

The mains on LED on front of filter still illuminates even if the input fuse is blown. The fuse is 3.15A, slow blow.

-5v FS5 blowing. Problem likely to be 2+2 card (leaky capacitors). Each 2+2 card should take approximately 40mA. Remove ALL 2+2 cards but one. Replace FS5 with a meter on ma setting. Check current, if over 40mA replace the card. Check each 2+2 card in turn as often more than one is faulty.

Digit splitting when used with Venue 24 and 700 type telephones.

Intermittent no incoming signal, when programmed for manual ring. Found to be 20 second line-out period on manual ring programme. If an incoming call is answered and released within 20 seconds and another incoming call is received within 20 seconds of the last call being answered, the navigator will not respond to the ringing current.

Internal view of the Navigator 16


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Last revised: November 04, 2021