TELECOM ACCESS STANDARDS NEWSLETTER NO. 86 December 1995 CONTENTS 1. CALLER DISPLAYS 2. PNR COMPATIBILITY WITH CALLER DISPLAYS 3. LINE CURRENT 4. CORDLESS TELEPHONE PTC REQUIREMENTS 5. ALARM AND SECURITY SYSTEM TELEPERMITS 6. "VOICE IN DATA" MODEMS 7. ELECTRICAL SAFETY TESTING OF MODEMS 8. ALPHA-NUMERIC KEYPADS 9. REVIEW OF YEAR'S ACTIVITIES 10. BUSINESS DURING HOLIDAY PERIOD 11. SEASON'S GREETINGS RETURN TO MAIN INDEX 1. CALLER DISPLAYS By now, most readers will be aware of the recent announcement by Telecom of an initial 3-month "pilot" to be held in the Greymouth area next February. The service I referred to in earlier Newsletters as "calling line identification" and "analogue caller ID" is now to be marketed by Telecom as "Caller Display". The network signalling protocol was published in July as a draft of Sections 10 and 11 of TNA 102, but we did not publish PTC requirements for the various types of display devices likely to be used with this service. The final PTC requirements are likely to be dependent on the results of the Greymouth pilot, which is planned to extend over three months. However, work to date has revealed some important design points that need to be considered on future display supplies and a draft section of the new PTC 200 is now being published to explain the provisional requirements. This will give potential suppliers the opportunity to consider the design issues. This draft is available from Access Standards at a price of $15, inclusive of GST and postage. Our technical staff have been trying out some existing overseas designs over the past few months and a number of issues have come to light. One purely practical issue likely to affect suppliers and Telecom is how the customer knows what to do when a display apparently ceases to function. Is it a display problem, a user problem, or a network problem? As far as the customer is concerned, it simply doesn't work, so who do they call? This leads to the need for some design improvements and for information to be made available to Telecom service staff if we are to avoid unnecessary product returns or service calls. For example, some form of "battery low indicator" signal is really needed. As long as the customer can see that it is a flat battery and not a fault, the battery can be replaced without calling Telecom or bringing the display back to the retailer with the complaint that it is faulty. A similar problem has been observed with some liquid crystal displays. Should the customer adjust the contrast for one light condition, it has been found that the display might virtually disappear under other light conditions. This again might prompt some customers to think there is a fault when it is simply a matter of adjustment. In some cases, we have found that display contrast may be inadvertently turned down by hitting the wrong control button. We recommend that User Instructions for any displays with this characteristic should give a clear warning of the need to check the contrast setting. The desirability of 15-digit displays was mentioned in the July Newsletter. International numbers will no doubt be available from many countries in the future and, as such numbers can be as long as 15 digits from 1997 onwards, we recommend that display units be capable of handling these number lengths. "Full length" displays should also avoid problems caused by the called party calling back the wrong number. For example, if a number is displayed on a typical US market device as "6127188887", it could fairly be assumed to be a Sydney number when it is really the US number "16127188887". The potential combinations of this type are quite frightening, as all country codes with "0" or "1" as the second digit could get muddled with North American Number Code Areas! Of even more concern to our customers, with such high traffic rates between here and Australia, is the loss of a digit on 10-digit displays now that Australia is converting to 11 digit international numbers. We always hold in confidence all information supplied to us as part of a Telepermit application, but we propose an exception with Caller Display units. We will be inviting applicants to authorise us to pass on specific details of the display characteristics to our service staff. These include the nature of the battery low indicator and what happens under specific number availability conditions. We are also interested in knowing whether provisions are made for self-checking the display, and how a number is shown when it exceeds the display capacity. For example; is it scrolled? Are only the initial digits displayed, or are only the last-received digits displayed? Other relevant data, includes the display format and control for time and date. Our aims are to be able to deal with as many as possible display fault calls over the phone. Should a Telecom service person actually called to the site, a quick check of the display functionality should be possible if its design characteristics are known. We suggest that this information be made available to our service staff and, perhaps, to our "120" and "125" Faults Service receptionists. Hopefully, we can then sort out a lot of apparent problems "by phone" and avoid the need to call out Telecom staff. From the suppliers' viewpoint, these arrangements might also avoid a lot of products being returned to their retailers to sort out. 2. PNR COMPATIBILITY WITH CALLER DISPLAYS As mentioned in earlier Newsletters, we have been concerned at the potential for PNR decoders to block the analogue caller display signals that follow the first cadence of ringing. The timing of the analogue caller display signals varies according to the cadence being transmitted, but it is not known which Distinctive Alert is actually being sent from the exchange until the end of the first cadence. This situation will get quite complicated once all four DA's are brought into service. Since some customers are bound to want both PNR and Caller Display on the same line, we have been trying to think of ways in which decoders could avoid blocking Caller Display signals. To cover the situation where a Caller Display device is connected across the line "behind" a decoder, the decoder could be designed to block and clip the 25 Hz ringing until it has decoded the cadence, but pass the low voltage voice frequency caller display signals through to all of the decoder's switched outlets. Initial considerations indicate that this approach may be a key to avoiding the blocking problems that have been concerning us. Comments and suggestions from designers and any other interested parties will be welcome. 3. LINE CURRENT These days, Telecom, like most overseas telecommunications administrations, is making quite wide use of derived systems within its local network reticulation. These allow existing copper pairs to serve two or more customer lines. As mentioned in Newsletter No. 73, we are constrained to buy equipment designed for the world market. It would be very costly to have "special NZ requirements" incorporated into these systems because our demand is very low in world market terms. The prevailing industry standards provide for only limited voltage or line current, typically only 20 mA to each derived line. Even this current may be reduced to around 18 mA when the system is operating on reserve battery. In comparison, our NEAX exchanges are designed to current limit at around 60 mA. This 20 mA does not restrict a customer's use of the line under normal operating conditions, as the great majority of modern CPE is quite capable of working properly at this level. However, as more and more derived systems come into use, more and more customers are likely to detect the impact of this current reduction in what might be termed "loss of fortuitous services". The one most likely to be noticed is the simultaneous use of two telephones. Direct off a NEAX exchange, the current is usually adequate to power two telephones. The customers may almost deafen one another when they speak, but both phones can be operated if the users accept the degraded transmission. Telecom does NOT design its network for such parallel operation, but some customers do make use of it from time to time. With the current limited to 20 mA, it may no longer be possible to use two telephones simultaneously as neither may get enough current to "turn on". As far as Telecom is concerned, handover between telephones on the same line should usually be possible, but we can no longer guarantee such "dual operation" on any lines. Suppliers should be aware of this situation in the event that their customers claim that CPE is faulty because it does not work on line with some other device. 4. CORDLESS TELEPHONE PTC REQUIREMENTS We are incorporating cordless telephone requirements into the "general purpose" analogue CPE specification, PTC 200. These will be the same as the guidelines we published some years back, other than for the following improved security requirements. Our original requirement was that cordless telephones should provide at least 256 security codes to prevent the "stealing" of dial tone. Since that time, suppliers have addressed the security issue far more liberally and all cordless telephones granted Telepermits over the past couple of years have provided thousands of possible security code combinations. In the circumstances, we intend to increase the minimum number of codes provided to 1000. Some cordless telephones provide a security code regeneration facility in the event that the original code is lost. This could happen if the batteries in the handset have failed or if they have been removed. For any cordless telephones with such a regeneration facility, we will require that the new code generated is truly random and not generated as a default number for that particular make or model. We have already experienced some problems related to this sort of practice. As they seriously inconvenience our customers and any service staff called in to sort out the consequential "crossed lines", our aim is to avoid problems of this nature in the future. 5. ALARM AND SECURITY SYSTEM TELEPERMITS We are making a determined effort to reduce the problems being experienced by our service staff due to series-wiring and hidden connections, as discussed in Newsletter No. 84. Also, there have been several complaints from local suppliers that there is still a lot of non-Telepermitted security equipment being connected to the Telecom network. As a result, I recently wrote to approximately 50 alarm monitoring companies to explain the legal implications should they allow non-Telepermitted equipment to be connected to their systems. I also asked that they refuse to connect such equipment after, say, 1 April 1996. We are planning to set up a system for recording connection locations at all existing locations where the installer or servicing company is willing and able to supply the necessary information. Preliminary discussions with a few alarm company representatives indicate that this will be a welcome move for all concerned, as it might help avoid inadvertent interference between services. On the other hand, recording such details for thousands of installations will be quite a major task, so we are seeing what can be done to effectively and efficiently fit this data collection into our internal maintenance database systems. I hope to be able to put some proposals to the alarm industry in the New Year. 6. "VOICE IN DATA" MODEMS A relatively new trend in the modem market is the provision of a voice plus data feature so that an associated PC equipped with a sound card and associated speakers can be used as an answering machine, or even as a loudspeaking telephone. Telepermit requirements are currently published in PTC 211 and PTC 212. A primary requirement is that where the modem simply switches an associated telephone to line for telephony purposes, the switching is not to introduce additional loss or impact on the transmission performance of that telephone. An even newer trend is the facility for digitally encoding speech and passing it via the modem as a combined speech plus data signal. Actual speech quality will depend on the encoding scheme and bit rate used. Because standards for this form of operation are still proprietary, this feature is usually feasible only if the called party has the same type of modem. In view of this, our initial approach to these devices for Telepermit purposes is to treat them as a form of "private network". If users need to have matching devices, they are obviously aware of any shortcomings and they can make the choice as to whether or not they wish to continue with a voice plus data call or simply drop back to speech only using conventional telephones. In this respect, we are also regarding them very much like a loudspeaking telephone in that we do not require any formal testing of the encoding feature. We will review this initial approach as services develop and industry standards come into force, especially where international traffic is involved. In the meantime, we expect to adopt the above approach when dealing with Telepermit applications for this class of product. 7. ELECTRICAL SAFETY TESTING OF MODEMS We now regard IEC 950: 1991 (AS/NZS 3260: 1993) as the primary international electrical safety standard for telecommunications equipment. This standard specifically covers "information technology equipment which is intended to be connected to a telecommunications network". As a result, it should be applied to line interface cards mounted within computer equipment. However, we have the problem that many PC cards are designed for the US market, where electrical safety standards are not as stringent as the international ones adopted by New Zealand and Australia. The following outlines the position with regard to the safety test requirements of PC cards. By the way, I use the term "PC" to mean any small computer, not just "IBM compatibles":- (i) Electrical safety testing of PC cards With mains-connected desktop PC's, where the cards are housed within an earthed metal cabinet, we have required 1.5 kV isolation between the telecommunications line and any earthed metalwork or between the line and any internal computer circuitry. This aligned with PTC 101 and was published as clause 2.9.3 (4) in Amendment No. 1 to PTC 211 in 1990. There was a similar amendment to PTC 212 at that time and we have since used the same text in the draft of PTC 202. A recent case has brought the need to align the above requirements with the international standard. Actual tests are to be made in accordance with AS/NZS 3260, but the requirements of its relevant clauses may be briefly summarised as follows:- a. Protective earthing applies to PC cards mounted within a PC chassis and the PC is regarded as "pluggable equipment type A". With rated voltage applied between the bonded telecommunications line input leads and protective earth, clause 6.3.2 requires that the current flow with any capacitors and surge suppressors in place shall not exceed 10 mA. b. Separation is required between the telecommunications network conductors and any parts that can be touched with a test finger or any circuitry (other than that carrying telecommunications signals) which connects to other equipment. The level of separation shall be checked either by an impulse test to 1.5 kV OR by an electrical strength test with a 50 Hz or 60 Hz sine wave ac rms voltage rising to 1.0 kV for a duration of 60 seconds. Alternatively, a dc voltage equal to the peak ac value may be used. There shall be NO breakdown of insulation. PTC 101 will be revised along the above lines and PTC 211 revision is being included in the development of PTC 200. In the meantime, test laboratories are advised to apply the above requirements for Telepermit testing purposes. Any suppliers intending to have PC cards tested for the Australian market should note the Australian amendments to IEC 950, which are published in the Appendices to AS/NZS 3260. These require that BOTH tests to clause 6.4 be carried out on product being submitted for AUSTEL permits. Also, the test voltages are increased. (ii) Electrical safety testing of parts that may be touched in normal use More stringent requirements apply to the separation between the telecommunications network conductors and any electrically conductive but unearthed parts that may be touched during normal use. Typical cases are telephone handsets and headsets, metallic control buttons, etc. Clause 6.4 of IEC 950 requires that such parts are to be checked either by an impulse test to 2.5 kV OR by an electrical strength test with a 50 Hz or 60 Hz sine wave ac rms voltage rising to 1.5 kV for a duration of 60 seconds. There shall be NO breakdown of insulation and any surge suppressors SHALL NOT operate. This requirement applies to products submitted for Telepermit. Again, the Australian requirements are even more stringent because of their much higher lightning incidence. The impulse test voltage is increased to 7 kV and the electrical strength test voltage is increased to 3 kV to meet AUSTEL requirements. In all cases, readers should refer to the Standard for further details of the test procedures. (iii) Voice/data modems This relatively new class of modem, especially the very compact PCMCIA versions, introduces another complication in the safety compliance issue. Typically, they switch an associated telephone handset between the line and the modem using a compact printed circuit board mounted relay. To power the telephone, this relay has a changeover contact set with TNV (the line) on one contact and ELV or SELV (from the PC power supply) on the other. The compact nature of the relay means there is very limited creepage and clearance distance. As a result, the relay fails the separation test in (i) (b) above. While we are reluctant to place a ban on these modems when the lower breakdown voltage does not represent a safety hazard to the user, there is greater probability of damage to the user's equipment and a higher risk of backfeeds into our lines. Most Telecom lines are now underground and rarely subject to high voltage surges, but surges are possible and they do occur. Serious consideration was given to the possibility of accepting a reduced breakdown voltage and requiring the supplier place a warning label on any products concerned. As far as user safety is concerned, a warning notice would align with the usual warning to disconnect the computer from the 230 V supply before opening the case. It would also advise the customer of the shortcoming in compliance with the Fair Trading Act. However, knowingly failing to comply fully with the relevant safety standards could be a legal liability for suppliers in the event of an electrical accident or any claims for compensation should the customer's equipment be damaged. In the circumstances, we will continue to require full compliance with the isolation requirements of AS/NZS 3260. However, suppliers should note that the test values are lower than those currently published in PTC 211 and PTC 212. These PTC requirements will be aligned with the international standard in the forthcoming PTC 200. 8. ALPHA-NUMERIC KEYPADS It is good to see an accelerating use of the world standard alpha-numeric keypad markings on new CPE items. A number of telephones, several fax machines and cordless telephones granted recent Telepermits now show the new keypad markings. It is interesting to note that reconditioned second-hand telephones being imported from the UK also have the new markings. Their use on new products and wider use of alphas for 0800 and 0900 telephone "numbers" are expected to promote customer demand for alpha-marked keypads. The internationally agreed "support date" of 1 April 1996 is getting close, so come on CPE suppliers, get those keypads marked so your products also support the use of alphas. Our number allocation people are observing increased requests for these "numbers", so be warned and be prepared or you may lose some sales! 9. REVIEW OF YEAR'S ACTIVITIES This year has seen a big upsurge in Telepermit applications. As at mid-December, we had received 481 applications and issued a total of 585 Telepermits and 42 Limited Permits. This is around 15% up on last year which was itself over 50 % up on 1993. Typical examples are Richard granting his 260th PTC 211-series permit on 15 December. This compares with 210 for the whole of last year and 132 the year before. Peter's telephone Telepermits are running at four times last year's rate! ISDN products were up from 28 last year to 64 this year. Obviously, the CPE business is flourishing. The end of the year saw two new services announced; Distinctive Alerts and Caller Display. Both look as if they are going to spawn a wide range of new and innovative products. We look forward with interest to see what our suppliers can come up with in the way of new products and ideas during 1996. 10. HOLIDAY PERIOD Access Standards will be on limited staffing over the Christmas/New Year period. The whole office will be shut down from early afternoon of 22 December until 2 January. Jenny and Richard will be available to deal with general enquiries from 2 January and the full team will be here from 8 January. Voice mail, correspondence and fax messages left during the break will be attended to on our return. 11. SEASON'S GREETINGS Peter Wheeler, Richard Brent and Jenny Hok join with me in wishing our readers and customers a happy and successful Christmas/New Year break. We look forward to hearing from you all again next year. We hope you have found these Newsletters useful and that they are keeping you in touch with Telecom's network changes. If not, write in and let us know. DOUG BURRUS Manager Access Standards