ISDX 300

PXML No. 47
APPROVAL No. NS/3343/123/C/021308 and NS/123/F/450980 DDI

Stored Programme Control digital PABX using Time Division Multiplex for switching and Pulse Code Modulation of speech, or data signals for transmission of information.

The 3000 maybe either single or multi-cabinet working, and is usually driven by two processors (one On-line, the other on Standby) but can be supplied with one and comes with a single 8 inch Floppy Disk. The 300 is always housed in a single cabinet and has a 3.5 inch floppy disc drive. Both may be fitted with a Winchester Unit with a 10 Meg 5.25 inch floppy, which contains the System Operating Program and Off-Line Diagnostic Programs. Later models are also fitted with a (Delta) data highway where DPNSS is a facility.
The optional service printers/terminal are GE Terminal 203D, BT M1220 or VT 4200.

Several standard power arrangements have been approved for use with the ISDX. These consist of various combinations of rectifier and battery eliminator units.
There is also a modular version, the Power System 2008b, intended for use with the BT ISDX range.
Made by GEC Plessey Telecommunications Ltd (GPT) (originally made by Plessey)
Technology Drive, Beeston, Nottingham. NG9 1LA

Distributed by GPT, BT and Mercury.

Installed by:
British Telecom PLC. Mercury Communications Ltd (MCL) - previously known as Telephone Rentals (TR).
GEC Plessey Telecommunications Ltd (GPT, formerly known as PCS).

System known as:-
Telematic DX MCL (TR).
Plessey IDX PCS.

Fully approved for connection to Public Switched Telephone Network. Fully approved for competitive maintenance.
PXML No. 47 issue 020 or later; F/HAM (Firmware/Hardware Masterlist) and SPAM (Software Masterlist) - both of which are associated with later PXML, detail the approved facilities, features, hardware and software versions.

Routine checks should be carried out as described in Part 2 Section 2 of the system Maintenance Manual 871/HA/20143/000, or Part 4 of the Service Manual 871/HA/20289/*** at the intervals specified.

The customer has the ability to change the software affecting a number of system parameters, e.g. Class of Service, Moves and Changes etc. For this reason a DUMP of these changes onto the System Disk and System Backup Disk must be done on a regular basis. A 3 monthly routine is recommended, but this may have to be performed more frequently if the customer requires it depending upon the number of changes being made; under these circumstances a charge may be made.

The customer's Named Representative may also, at the discretion of the Registered Maintenance Authority (BT), have access to some, or all, of the Level 1 maintenance commands on an individual basis, after suitable training.

Connection or a 50v DC power supply to the PSU input for a period or not less than 16 hours every 6 months is necessary to maintain spare PSU's in reliable working condition. No load need be applied.


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Last revised: December 22, 2021