TELECOM ACCESS STANDARDS NEWSLETTER NO. 158

December 2005

CONTENTS
1. GENERIC CABLING FOR NEW HOMES: PTC 106
2. TELECOM 2-WIRE JACKPOINTS – DESIGN CHANGES
3. USE OF EXTENSION CORDS WITH BROADBAND MODEMS
4. ADSL DEVELOPMENTS
5. CHRISTMAS GREETINGS (AND FAREWELL?)
RETURN TO MAIN INDEX



1. GENERIC CABLING FOR NEW HOMES: PTC 106

PTC 106, our draft Code of Practice for Residential-Type Generic Cabling Systems, is now available for public comment. This addresses the overall cabling of new homes, sets requirements for installation practices and makes a number of recommendations. This draft document is free of charge and is now published on our website under “on-line specifications”.

Comments and suggestions on the draft will be welcomed.


2. TELECOM 2-WIRE JACKPOINTS – DESIGN CHANGES

As indicated in the last newsletter, ITT-Cannon have advised that they are ceasing production of their enhanced plated BT 601A or 605A sockets. We have been working with ModemPak (the manufacturer of Telecom’s own jackpoints) and MPT Laboratories Ltd to select and test a suitable replacement socket.

Following an initial series of accelerated life tests of a range of different design options, we arranged further tests of the current Telecom jackpoint (with the 6-pin ITT-Cannon socket) and the proposed new version with only two contact springs and no capacitor. These tests are continuing, but have so far shown a significant improvement in expected service life if we go to a 2-contact socket and no longer provide the ringing capacitor within the socket.

The only disadvantage with the new design is that the few remaining 3-wire telephones in service will need to be catered for. There are several options. It is expected that corroded jackpoints will still be replaced with the present design until stocks run out but, in any cases where it is necessary to replace an existing jackpoint with the new version, these older telephones can be connected via an adapter with an integral capacitor. Otherwise, older telephones rented from Telecom can be replaced by a newer version, or be left in “non-ringing” state if customers have other telephones and do not need the old ones to continue to ring.

Most replacements in homes and small businesses are carried out by Telecom contractors who will advise the customers of the change and supply the most appropriate option. Where an adapter is provided, this can be associated with the phone if it is moved to another “2-wire only” jackpoint.

We are now revising both the TNSP Specification (which defines Telecom’s more stringent requirements for its own jackpoints) and PTC 223, which defines the Telepermit requirements for jackpoints made by other suppliers. In addition to the specification changes affecting the actual jackpoint, there will also be a requirement for placing a simple warning notice in retail jackpoint packaging regarding the need for an adapter with older type telephones.

Currently, we are proposing to refer to the new jackpoint as “2C” (two contact) to differentiate it from the existing “2-wire” version and to mark the new ones accordingly. Although PTC 223 will be the relevant specification for both types, Telepermits will be granted in a new PTC 233-series to help make users aware of the different design and its lack of support for older type telephones.

Telecom’s supplier of the new 2C socket is able to provide them to other jackpoint manufacturers, but if this is not acceptable for some reason, other suppliers’ sockets can be subjected to an equivalent comparative life testing programme. Any such sockets that prove to offer the same or better levels of reliability can be included in PTC 223 as “acceptable components” in due course.


3. USE OF EXTENSION CORDS WITH BROADBAND MODEMS

Broadband modems operate at frequencies well into the AM broadcast band. As such, the potential for the broadband signals to cause interference to the radio signals from distant AM broadcast stations was of concern when we first introduced our ADSL-based services. So far, we have not had many reports of such problems.

One problem that has come up from time to time is interference with the broadband modem when long extension cords have been used. Our preference is to avoid these cords altogether or, at least keep cord lengths to the minimal length. In a recent case, the customer had a long cord housed in a cord caddy and this was shown to have picked up enough external interference to upset the modem.

Telephone extension cords are primarily intended for voice band applications. They do not commonly use twisted pair wiring, but have straight parallel wires over their full length to facilitate easy machine termination. Unfortunately, this makes them fairly effective antennas for both radiating the ADSL signals and picking up any local interference from appliances or other signal sources.


4. ADSL DEVELOPMENTS

We have been discussing the need for tightening our ADSL PTC Specifications with Alcatel, our network equipment supplier. As advised in earlier Newsletters, the service performance experienced by our broadband customers varies quite widely for a given line loss. The bit rates achievable with ADSL are expected to reduce with increasing line loss, as this is inherent in the design. However, network analysis equipment has shown very wide variations for customers with the same line loss.

This variation can be due to a range of different factors, which include line noise (gradually increasing as we add more ADSL customers to our cables), poor home wiring, local interference from electrical transient arising within the premises, lack of sufficient line filters, or modem performance. As far as this last item is concerned, we have already commented on the impact of on/off-hook transients and ringing voltage as possible causes of frequent re-starts observed in earlier network surveys.

Most residential customers are operating at 256 kbit/s, so potential below par performance will not be apparent to the user. However, when we come to needing faster operation for next generation services, it is expected that any shortcomings will become more obvious.

Our aim is to tighten up requirements PTC 270 for modems, PTC 280 requirements for filters (covering performance at ADSL2+ operating frequencies, as one aspect) and to publish a new PTC 281 for centralised splitters suitable for premises with generic cabling.

More on these matters will be published in 2006.


5. CHRISTMAS GREETINGS (AND FAREWELL?)

Another year of Telepermitting has passed with a steady and even increasing flow of products over a wide range of technologies. Voice over IP systems, telephones and PABX “Add-ons”, broadband modems and cordless phones have been amongst the most prevalent this past year. It is interesting to note that Telepermits for cordless phones during 2005 (base stations and handsets) outnumber wired phones just over 8:1, a good example of how the technologies and relative prices have been changing over the years.

Looking back over the Telepermit grants since the CPE market was opened to competition, a total of 8745 grants have been made. Access Standards have not been involved in the mobile handset area, which is dealt with by our colleagues, but our own score is now well over 8000, showing that local customers have not been short of choice. Following several years of gradual reductions in Telepermits granted, largely due to the drop-off in dial-up modems, this year saw an increase to 577 different products gaining Telepermits. The main contributors were the product types mentioned above.

I have been involved with Access Standards from the start, but it is now time to call it quits and retire. I expect to be finishing with Telecom in January. Whether or not I will be back from time to time for “special projects” is a possibility, but this is probably my last Access Standards newsletter.

I would like to take this opportunity to thank CPE suppliers for their patience and co-operation over the past 18 years or so. In this time, we have dealt with hundreds of different people representing importers here and suppliers overseas, plus our accredited test lab staff, all of whom have helped keep the system rolling along.

It is good to look back and note that we have suffered very few problems due to CPE being incompatible with our networks, despite the large number of products that have been and still are in service.

I and my team, Richard Brent and Alan Reedy, wish all our readers a Happy Christmas and a very successful 2006.



Doug Burrus
Manager
Access Standards