TELECOM ACCESS STANDARDS NEWSLETTER NO. 157

October/November 2005

CONTENTS
1. ACCESS STANDARDS ORGANISATIONAL CHANGES
2. ISDN PRIMARY RATE “LITE”
3. GENERIC CABLING FOR NEW HOMES: PTC 106
4. TELECOM 2-WIRE JACKPOINTS – DESIGN CHANGES
5. BROADBAND IMPACT ON MEDICAL & SECURITY ALARMS
6. WITHDRAWAL OF BOTHWAY ANALOGUE DDI
RETURN TO MAIN INDEX



1. ACCESS STANDARDS ORGANISATIONAL CHANGES

Since its inception, Access Standards has primarily dealt with what is now termed the “wireline” side of Telecom’s networks, with actual compliance testing carried out by independent laboratories here and overseas. A parallel operation has been in place for Telecom’s mobile networks, but with one significant difference. For mobile CPE, Telecom has always carried out at least some of the testing itself, originally to make sure overseas tests to FCC requirements are fully applicable here. The amount of Telecom testing has increased since its CDMA mobile network was established due to the much closer integration between the mobile handset capability and the multiple services deliverable by this network.

One thing becoming clear from the way technology is developing is that “convergence” between wired and wireless devices is rapidly coming to the fore. From the simple cordless telephone connected to an analogue line a few years ago, wireless products have evolved to digital cordless PABX’s, Wi-Fi for VoIP telephones or LAN’s connected to broadband internet. On the other hand, mobile handsets will be able to act as PSTN telephones in the home or in the customer’s own business premises, and automatically revert to mobile phone operation when out of range of any “home” locations.

This “convergence” is being recognised by merging the resources and activities of Access Standards with those of the Mobile PTC team. The joint team’s new formal title is “Divisions Device Integration”. Access Standards’ role will be unchanged. However, the merger should help in developing PTC specifications for the new generation of “converged” CPE.

The group as a whole will continue to operate at “arm’s length” from Telecom’s own CPE business, with the aim of ensuring that all CPE connected to Telecom network(s) is compatible with those network(s).

Access Standards has been re-located to Unit 4 of the Telecom Centre at Tory Street and we now have a new fax number (04) 801 7496. Otherwise, the earlier contact details are unchanged.


2. ISDN PRIMARY RATE “LITE”

Telecom will soon be introducing a new ISDN Primary Rate Interface (PRI) to the New Zealand market. The new equipment will complement Telecom’s existing ISDN network equipment, as NEC no longer manufactures the NEC-supplied ISDN Network equipment.

Telecom has worked closely with NEC in the interface of the new ISDN PRA service to ensure it complies with our ISDN PTC and TNA specifications. This means that Telepermits already granted for customer ISDN equipment will be unaffected.

However, there are differences in the feature set offered by the two services. The new interface has a limited feature set, keeping only those features most commonly used by Telecom’s ISDN PRA customers. Research noted that many existing customers focused on the benefits offered by the digital network interface rather than the wide range of options available on the service.

The features kept on the new ISDN PRA service are:

* CLIP – caller line identification presentation (this is always on)
* CLIR - caller Line identification restriction
* DDIPG – direct dial in for primary group
* ISDN Date and Time
* Non-code access – for PSTN national, mobile and international calling via network using pre-selected operators other than Telecom for these services.

NOTE: Other than for the reduced feature set, there are two other differences:

* At this stage, the Lite service is available on only one PRI link and it is not possible to couple two or more PRI’s into a single number group or share the D-channel signalling; and
* This “Lite” solution will NOT provide for dial tone be supplied from the network.


3. GENERIC CABLING FOR NEW HOMES: PTC 106

Telecom’s packet-based “Next Generation Network” (NGN) will be delivering a steadily increasing range of services, many of which will be based on Ethernet distribution around the home or business via what is termed “Multi-Service Single Access”. This entails provision of an interface “box” at the customer’s premises, which will accept from and deliver to the public network a packet mode digital bitstream. In time, this will replace the “traditional” analogue voiceband POTS services.

Existing POTS CPE can be supported by Analogue Telephone Adapters (ATA’s) either as stand-alone devices or ports on the network termination equipment.

This new mode of operation will support multi-media services, not only those currently provided over the present ADSL-based broadband access, but also such services as IP-TV. The common term for these new services is “Triple Play”. Once the Telecom network provides an IP interface, IP telephones will also be available more widely and become an attractive option. They can be expected to reduce in price and increase their features.

For existing homes, our current premises wiring practice via the 2-wire jackpoint will not be capable of supporting all of these new services without some sort of additional technology, such as wireless (typically WiFi) or add-on boxes (HPNA over the phone wiring, or HomePlug over existing 230 V power wiring). These may be the best options for many customers, as replacing the existing telephone wiring when walls and ceilings are completely lined can be quite expensive.

New homes are a different proposition. Installing cabling is a relatively low cost and easy task in a new building if it is carried out before the framing is lined. Also, of course, cable is reliable and secure and offers fairly high bandwidth – especially over the typically short cable runs encountered in most homes. Cable is also capable of supporting a wide range of services, not just those available from the Telecom network. The term “generic” in reference to such cabling indicates that it is installed in a standard way, independent of whatever services might be carried over it.

Unfortunately, a lot of new homes are still being “2-wired” with 2-pair cable looped from jackpoint to jackpoint. Similarly, few homes have much coaxial cabling installed for TV and video distribution. A common problem for SKY Network Television is that customers only subscribe to their service after they have moved into a new home. No thought has been given at the building or design stage as to where the satellite dish is to be installed and how it is to be cabled to the decoder and its associated TV set.

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

Comments and suggestions on the draft will be welcomed.


4. TELECOM 2-WIRE JACKPOINTS – DESIGN CHANGES

PTC 223 specifies that the socket component of our 2-wire jackpoints shall be the “enhanced plating” version of the ITT-Cannon BT 601A or 605A socket. We decided to use these particular sockets after experiencing serious corrosion problems with the various makes of sockets used earlier.

As the result of several years of practical experience with these ITT-Cannon sockets in the New Zealand environment, we were satisfied that they, in combination with our 2-wire jackpoint design, have greatly improved long-term reliability. However, “all good things come to an end” and ITT-Cannon have now advised that they are ceasing production of these sockets. We are now working with ModemPak (the manufacturer of Telecom’s own jackpoints) to select a suitable replacement socket.

This change in socket component provides an opportunity to make some further changes, one of which has been contemplated for some time. The present 2-wire socket incorporates a 1 microFarad capacitor to support a 3-wire telephone (one that originally relied on the common ringing capacitor in a Master 3-wire jackpoint). These telephones have gradually been replaced over the years and there are relatively few still in service. Also, new designs of 3-wire telephone have not been introduced for at least 10 years. As a result, it is no longer cost-effective or necessary to include a 1 microfarad capacitor in every 2-wire jackpoint. We are working with ModemPak to introduce a “2-wire only” jackpoint with no integral capacitor. The few remaining 3-wire telephones in service can be supported by an add-on adapter should it be necessary to replace an existing jackpoint with the new version.

The proposed “2-wire only” jackpoint offers further advantages as regards both cost and improved reliability. Instead of the standard 6-contact spring BT socket, we are investigating the possibility of specifying and purchasing a 2-contact spring version, with contacts only at positions 2 and 5. This provides increased clearance between the contact springs with 50 V across them. It is also expected that the 2-pin socket will be a little cheaper to produce. Using only 2 pins will also allow greater clearances between the tracks on the printed circuit board. These changes should further reduce the risk of insulation breakdown and corrosion in damp conditions – a common cause of service disruption for our customers.

With the introduction of these “2-wire only” jackpoints, there is a risk that customers will connect a 3-wire telephone and find it no longer rings. Most corroded jackpoints are replaced by Telecom contractors under our Residential Wiring maintenance service, so an adapter can be provided where the telephone fails to ring. To make sure there is a visible difference between the present and new jackpoints, we are looking into a suitable means of marking the shutter or faceplate of the new versions to show that they do not support 3-wire phones. Needless to say, if the socket is in a position where the customer can easily raise the shutter and look into the socket, it will be clear that there are only two contact springs in place of the usual six.

Laboratory testing of these developments is now in progress and, once everything is finalised, we will be 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.


5. BROADBAND IMPACT ON MEDICAL & SECURITY ALARMS

There was a recent situation reported in “Fair Go” where it was initially suspect that Telecom’s broadband service had prevented the operation of an alarm dialler. In the case concerned, it was subsequently proven that the alarm system had not been set correctly, but this case did raise the issue of possible interference to alarm systems or diallers caused by high frequency ADSL signals.

The usual approach is to use line filters connected between the jackpoint and each item of analogue CPE when a customer gets broadband.

There are two exceptions for which it is necessary to install a splitter on the network side of all wiring and CPE connected to the line concerned within the customer’s premises;

* Where the customer needs more than 5 filters; and
* Where there is any sort of analogue device, such as an alarm, that is hard-wired (not plugged into a jackpoint) and thus cannot have a filter fitted.

The broadband signals from the customer's modem are at a much higher frequency than the traditional voiceband (mainly in the range 25 KHz - 138 kHz) and at a higher level. If the alarm control equipment and dialler is directly subjected to these signals, there is a possibility that their operation could be affected. Needless to say, alarm systems were in use long before broadband was introduced and they were never designed to cope with such broadband signals.

There is a possibility that some alarm system controllers or diallers could be affected if they are not fitted with a filter or splitter. Even then, this may not necessarily always occur with a specific system. The modem signal level is set by the DSLAM during the initialisation period, such that it may be decreased on short lines with low loss or increased on longer (higher loss) lines. Access Standards has not received any formal reports of such problems, but it is understood some have arisen from time to time.

The key point is that with hard-wired alarm systems, for which reliable operation may be a “life or death” matter, it is best to ensure that the necessary splitter is installed to keep the ADSL signal path well separated from that of the alarm system. By installing the splitter at the network demarcation point, Telecom can be sure that it is connected on the line side of any hard-wired alarms.

Non line-grabbing alarms that are plugged-in via a jackpoint still need a line filter, of course.  


6. WITHDRAWAL OF BOTHWAY ANALOGUE DDI

As explained in Newsletter No. 117 back in December 1999, Telecom's recent generations of access transmission systems do not support bothway analogue Direct Dialling-In (DDI).

The Telecom PSTN, like most overseas networks, has traditionally always aimed for backwards compatibility with existing customer equipment. As a result, some of our services are based on very old technologies and practices. For example, our reverse decadic dialling originally dated back to the 1920’s. Although it is rarely used these days, the Telecom PSTN still supports this mode of signalling.

Another such “legacy” service is analogue Direct Dialling-In (DDI), which allows a caller direct access to individual extensions of an analogue PABX. Bothway analogue DDI was to have been withdrawn for new customers some years back, when we first started purchasing access multiplex systems which do not support Bothway analogue DDI as part of their basic design. Unfortunately, it now appears that the service has continued to be provided for those parts of the network where there are lines that still support it. As a result, more customers have been provided with this service than we originally anticipated and they will be impacted when the Next Generation Network replaces the present NEAX network will be higher than we had expected.

Telecom is faced with two options: either call on manufacturers of new access and switching equipment to make special provision for traditional services like our analogue DDI; or face the fact that this technology is outmoded and start to withdraw this service.

This matter is again under consideration within Telecom and it is fairly certain that Bothway analogue DDI will no longer be offered to new customers some time in 2006. This decision will impact on PABX suppliers and the types of trunk interface cards they will be importing, so the above should be regarded as “a second early warning” of this change.

More on this subject will be published in future Newsletters.



Doug Burrus
Manager
Access Standards