TELECOM ACCESS STANDARDS NEWSLETTER NO. 95 NOVEMBER 1996 CONTENTS 1. WHAT NEEDS TO BE DONE TO INTRODUCE "CALLER DISPLAY" 2. "CALLER DISPLAY" - OUTLINE OF CPE-RELATED ISSUES 3. NEW CALLER DISPLAY CONTROL CODES 4. TELECOM'S NETWORK ARRANGEMENTS 5. CALLING CPE ARRANGEMENTS 6. CALLER DISPLAY CPE AND CTI SYSTEMS - DIALLING BACK PROBLEMS 7. SERVICE TIMING 8. ADVICE TO CUSTOMERS return to index NOTE: This Newsletter and its attachment explain in some detail the changes being introduced within the Telecom network to introduce "Caller Display" and their potential impact on customer equipment. In view of the importance of this issue to customers, CPE suppliers and maintainers, it is being dealt with as a special "one topic edition" of the Access Standards Newsletter. It is recommended that suppliers copy this Newsletter to all those people within their organisations who are involved with the programming of their customers' equipment. 1. WHAT NEEDS TO BE DONE TO INTRODUCE "CALLER DISPLAY" The introduction of "Caller Display" will include use of optional number presentation control prefixes on a call by call basis. To maintain the integrity of PABX toll barring, PABX suppliers and maintainers will need to determine the digit analysis capabilities of their systems and whether any changes are necessary to handle these optional codes. Call Detail Processors will also need reprogramming to ensure continued accuracy of call charging. "Network Number Withhold" is available to cover any incompatibilities, but whether this is chosen depends very much on the capabilities of the PABX used. Telecom will soon be asking its customers to advise on their preferred network option and they will need help from those persons involved with the detailed programming of their systems. In view of this, Telecom now seeks industry support in arranging any CPE changes and advising customers on the most appropriate network option. Return to Contents 2. "CALLER DISPLAY" - OUTLINE OF CPE-RELATED ISSUES Service delay Telecom's Caller Display service was deferred during August following a pre-launch check of customer equipment compatibility and support arrangements. The following information is an outline of the privacy arrangements, the reasons for the delay and an explanation of what needs to be done to ensure a successful service launch. Only if CPE suppliers and maintainers are aware of all the following issues will they be able to deal with customer enquiries. Communication with suppliers Telecom staff will be contacting PABX and CDP equipment suppliers seeking their cooperation and information on the called number analysis capabilities of their equipment. The aim is for Telecom and CPE suppliers to be able to jointly advise customers on their options, which will depend very much on the capabilities and set-up of each customers' equipment. Display-capable CPE The Telepermit requirements for CPE used to display calling numbers are affected only as regards dialling back the calling number - See Item 6. Privacy Act requirements Caller Display must comply with the Privacy Act. Telecom's understanding of the Act is that it is important for ALL CALLERS to have the ability to restrict display of their numbers, should they wish to do so. Note that the privacy requirement applies to the caller, not just to the customer. Thus, even if the customer renting the line has stipulated that the number should normally be displayed, the caller must have the right to withhold the number on a per call basis. Current position The original display control codes would have disrupted the toll-barring systems of many earlier PABX systems. Telecom has now determined a solution, which involves introducing some new control codes and making changes within its network. If possible, Telecom hopes that other network operators will be able to use the same codes, as this will be easier for customers using different service providers. Telecom has communicated the proposed codes to the other carriers. Numbers displayed For individual line customers, the number that would be displayed to the called party is the area code plus the directory number. The national call prefix "0" is NOT passed forward by the network, but may be shown on some types of display (see Item 6 dealing with dialling issues). For extension to extension calls by Centrex customers, the number displayed will be their Centrex "extension" number, not the main company number shown in the Telephone Book. ISDN customers have the opportunity to provide extension numbers if their PABX has been set up to do so. Until that has been done, the number displayed will correspond with the particular exchange line (trunk) selected for the call. Again, the "pilot" or main directory number is not shown. For PABX customers, the "pilot" or main directory number of the company concerned (the one shown in the Telephone Book) will not normally be displayed. Instead, the number displayed is the number of the exchange line used to make the call. The number displayed will not relate to individual extension users and it will vary from call to call, depending on which trunk is used by the PABX. Nevertheless, unlike some overseas countries, privacy requirements still apply and the caller has the right to withhold display of the calling number, even though it is not a direct indication of the calling extension. Original Number Display Control codes now dropped In line with the principles announced in Newsletter No. 84, Telecom will be moving towards the adoption of "*" and "#" prefixes for many of its supplementary services. An early example was "*52" for suspending Call Waiting. Telecom was going to follow the same basic principles for controlling Caller Display. To meet the requirements of the Privacy Act, the codes "*67" and "*65 and the two equivalent 4-digit decadic codes "1867" and "1865" were allocated as Number Display Control codes. One or other of these codes would be dialled before the wanted number ONLY if the caller wants to over-ride the pre-set network display condition. For the following reasons: The original codes are NOT being used at this stage Problem areas i. PABX support Although the display control codes were announced some time back, it is now clear that their significance was lost on many PABX customers and system maintainers. Many PABX's are not set up to accept the "*" codes as initial digits of a called number and they simply reject such calls as invalid. Others may use a "*" prefix for other functions within the PABX. ii. Toll-barred extensions on PABX systems Most simple toll barring is based on detecting the first digits of the called number in the format "trunk access digit (usually "1") followed by the toll prefix digit 0". The use of the original optional presentation control codes upsets these simple barring systems. iii. "Simple" shop payphones Some "local call only" shop payphones have relatively unsophisticated toll barring features. Typically, when connected directly to an exchange line, they need to detect only the first digit as "0" in order to block all but local calls. When connected via PABX systems, this simple scheme is typically extended to "1, 0". Some of these payphones have been extended to check more than the first two digits to allow these "free to calling line" calls, such as "0800" and "0120". However, such phones would need further modification to cope with the original optional presentation control codes. iv. Call Detail Processors It should be noted that one or other Number Display Control codes will not always be dialled, but prefixing ANY call with a control code will impact on Call Detail Processor (CDP) programming. Unless use of the codes is taken into account, the assessed call charges will be inaccurate and toll or international calls may appear as "free of charge" service calls. Return to Contents 3. NEW CALLER DISPLAY CONTROL CODES Telecom's proposed solution to the above problems includes the use of a completely new set of presentation control codes. "Star" codes will not be used at this stage (but will be introduced after CPE suppliers have been given reasonable time to overcome current incompatibility problems). The new codes proposed are as follows:- For the caller to withhold number presentation on a call by call basis when the line is set to permit display of its number: "197" and "0197" To the caller to permit number presentation on a call by call basis when the line is set to normally withhold its number ("Automatic Number Withhold"): "196" and "0196" * The need for "code pairs" is explained below in relation to PABX toll-barring. Customers without toll-barring problems can, of course, simply use the "0196" or "0197" codes if they wish. * The two "star" codes are being dispensed with at this stage, mainly to keep the number of customer options down to two "pairs", but also to assist where PABX systems cannot currently handle public exchange calls commencing with a "star". Return to Contents 4. TELECOM'S NETWORK ARRANGEMENTS To avoid the above problems for CPE users and suppliers, Telecom offers the following network options:- a. "Display", with per call presentation withhold (restrict) codes The line is set up in the exchange so that the calling number is normally presented. Per call withhold is provided by means of the new override codes, as explained below. This is the option expected to be used by most customers. b. "Automatic Number Withhold", with per call presentation (display) codes" The line is set up in the exchange so that the calling number is normally withheld. Per call display is provided by means of the new override codes, as explained below. The following conditions apply for options "a" and "b":- The network will permit ONLY LOCAL and Free Calling calls after the codes "196" and "197" (e.g., "012", "0800" , plus "0508" in some exchanges). ANY type of call ( local, national or international, direct dialled or operator assisted) may be dialled after the codes, "0196" or "0197". For options "a" and "b", ONLY ONE control code may be dialled at the start of a call. The network will then return a second dial tone as an indication that the code has been received. Should a caller dial a SECOND control code, the call will be dropped. Should a caller dial a number withhold code when the line is set for "Automatic Number Withhold", the network will accept the call. Should a caller dial a number display code when the line is set for "Display", the network will return NU tone and the call will fail. * Note that this arrangement protects the simple toll-barring arrangements described above. Should the "0196" or "0197" code be dialled from a toll-barred extension, the PABX will block the call in the normal way. Such extensions can still use "196" or "197", as these are limited by the network to local calls only. Application Unless they have Call Detail Processors which need reprogramming or cannot be reprogrammed, the great majority of business and residential customers will be able to use one of these options. A third network option will now be made available on a per line basis for those customers with CPE compatibility problems. c. "Network Number Withhold" On those lines set up for "Network Number Withhold", the network will NOT accept any control codes. ....... 7. For option "c", should a caller dial any one of the presentation control codes, ........... the call will be dropped and the caller will hear NU tone. Application This option can be used by customers with any of the above compatibility problems or by any customers until such time as they have satisfied themselves that their switching equipment and call Detail Processors are compatible with the use of presentation control codes. Return to Contents 5. CALLING CPE ARRANGEMENTS Checking all PABX system capabilities, CDP re-programming and advising business customers of their best options will no doubt take some time. Until this work is done or where systems are not capable of being modified, the customer can use option "c", as explained above. This ensures that the caller's privacy is maintained. In the majority of cases, the existing PABX programming should be capable of supporting the new control codes, and the main task will be to confirm that Call Detail Processors are capable of accepting the optional control codes without upsetting their charging calculations. Where a PABX extension is international toll-barred, but permitted to make national calls, the network option chosen will depend on the number analysis capabilities of the PABX system. Return to Contents 6. CALLER DISPLAY CPE AND CTI SYSTEMS - DIALLING BACK PROBLEMS The above code changes relate ONLY to the control of number presentation by the calling party. This section deals with issues affecting the design and operation of the called party's display device. Display CPE suppliers should note that NOT all Telecom customers can subscribe to the Caller Display service. The majority of customers directly connected to our NEAX 61 E exchanges will be able to subscribe to this service, but there will be some exceptions for those served by derived line systems which cannot support the signalling arrangements. Customers served by other types of exchange will NOT be able to subscribe to the service. The basic signalling arrangements of display-capable CPE used by subscribers to the Caller Display service are unaffected by the network and control code changes. Nevertheless, there is a potential problem with any devices as regards dialling back the calling number. Automatic dialling back by devices that do not generate the "0" prefix for national calls or do not drop the area code for local calls will result in wrong numbers. * "Automatic" includes any device which can dial the stored number, even though this may usually manually initiated by a single key press. This situation can arise because the calling number display data passed forward to the receiving CPE by the network is in the format:- Area Code + Directory Number. There is NO "0" prefix. * This is covered in the note to clause 11.4.5 of PTC 200, which states that the format is "one digit area code plus 7-digit local number". This format applies for both local and national calls. It is important that all display devices are provided with instructions to explain how the number displayed relates to the number to be called. EXAMPLE: on most caller display devices a call from the Wellington number (04) 234 5678 would normally be displayed as "4 234 5678". On some units, there may also be one or more "-" symbols displayed to break up the number for easier viewing. Also, some display units insert the "0" prefix to show the "04". This fits with the normally published presentation format of showing a national number complete with the "0" national call access digit. DIALLING STORED/DISPLAYED NUMBERS a. Display devices that do NOT generate the "0" prefix Should the user manually dial the number, as it is displayed in the above example (including the area code digit, but omitting the "0"), the result would be "423 4567". Where the dialler provides a "Dial Back" facility, such that the user simply presses a key to have the display device dial the stored calling number, the wrong number will result, as in "a (i)" above, unless the dialling logic is able to discriminate between local and national numbers. This would require dropping the area code for local calls and adding the necessary "0" prefix for calls outside the local calling area. b. Display devices that DO generate the "0" prefix Should the user manually dial the number displayed, the number dialled will be correct, but there could be complications if Non-code access is implemented on the line (see below) Where the dialler provides a "Dial Back" facility, the situation is the same as for the manually dialled call in b (1). To work effectively in all cases, auto dial back devices should drop the "0" and the area code for local calls but include them on calls outside the local area. Such a feature is possible, but difficult to implement because the same area code will usually be common to several local calling areas. EXAMPLE: if a Wellington customer has a display unit with a dial back feature and the number displayed is "4 297 2487", this indicates a Kapiti customer. In this case, the Wellington customer does need to input the "04" to make the call. This situation applies for ALL Telecom area codes. It is particularly complicated for South Island customers because area code "3", is used for the whole of the South Island. INTERNATIONAL CALLS: International numbers are soon moving to 15 digits, as explained in Newsletter 94. The present generation of display units mostly offer only 10-digit capacity, as they were originally designed for the North American market. International calls are not an immediate problem, as the Telecom network forwards "0000" for international calls incoming via our Gateway exchanges. However, this is not necessarily the case for ALL international calls received by a Telecom customer, as some calls come in via other network operators. Should a display unit with auto dial back insert the "0" prefix, there is potential for problems when Telecom is finally able to present overseas numbers (which need the "00" prefix). It is not practicable in all cases to differentiate national from international by means of number length, as some international numbers will be shorter than our current national call maximum of 9 digits (252 xxx xxx). NON-CODE ACCESS: Most customers will be able to dial the "0" prefix and area code for all numbers displayed. However, care is required where the customer uses the services of other networks for toll or international calling. If calls from customers having non-code access to another network's toll by-pass service include the "0" prefix and area code for a local call, their call will automatically be diverted to the by-pass network. A toll charge from the other carrier may result. REVISED TELEPERMIT REQUIREMENTS: In view of the potential dialling back problems, devices with automatic dial back will NOT be granted a Telepermit unless they provide a solution to the above problems or permanently disable the dial back function. In addition, it will be required that clear instructions and warnings be given regarding calling back stored numbers. Other than for these issues, the requirements of TNA 102 and PTC 200 for the called party's CPE are not expected to be affected. WARNINGS TO PURCHASERS: In view of the above potential dialling back problems, it is recommended that suppliers check the operation of their display devices, explain clearly how dialling back is to be done, and suitably warn customers about any problems likely to result from their use. The necessary changes to PTC 200 will be published later, along with some other general changes in PTC requirements, which will be discussed in future Newsletters. COMPUTER TELEPHONY INTEGRATION: Computer Telephony Integration (CTI) has not been specifically addressed in PTC Specifications. Analogue CTI equipment needs to be compatible with the on-hook data transmission and calling line identification presentation signalling of Sections 10 and 11 of TNA 102. CTI equipment also needs to meet the related CPE requirements of Section 11 of PTC 200, subject to any changes resulting from the above automatic dialling back problem. ISDN CPE requirements are covered in TNA 135. The actual CTI application is not subject to PTC requirements. Return to Contents 7. SERVICE TIMING These additional options are being put in place within the Telecom network. However, in order to give customers and CPE suppliers time to check out their equipment and select the most appropriate option, Telecom's Caller Display service is expected to be delayed until early next year. Return to Contents 8. ADVICE TO CUSTOMERS In the near future, Telecom will be formally advising its customers about the revised Caller Display codes and the need to consider their CPE compatibility before deciding on the most appropriate network option. To assist CPE suppliers and any other parties involved in advising customers on such matters, a draft of the proposed customer letter is attached. The letter may be subject to editorial revision before it is formally released, but the main content should be accurate. On receiving these letters, it is likely that customers will contact Telecom and their CPE suppliers for further advice. Telecom staff will not usually be aware of the type of CPE used by each customer, nor will they know anything of its number analysis and barring capabilities. As a result, it is expected that CPE suppliers will have to take a significant role in preparing for the introduction of Caller Display by Telecom and other network operators. A successful service launch will obviously need close cooperation between Telecom and its CPE suppliers. In this respect, it will be appreciated if any CPE or operational problems not covered by the arrangements described above are communicated to Access Standards. 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