__ __._____._____:_____._____._____._____:_____._____._____ : Y : _ : _ Y_ _ : _ : . : ___Y __ : . : ____: --------| _ | _ | | _/ ___j _ | | l___ | \_ | | | \_ |-------- _\\//_ | : : : : : | L : | :__: : | | / : | : | : _\\//_ (_o,O) `--'--'--'--'--'--^-----'--'--' `--'-----^-----'-----'-----' (O.o_) " " Emergency and Code Only Document for TXE4 Exchanges " " Concerning Call Routing for 999 and 112 Typed by sTALKEr of MED This Document will attempt to bring together all the information on emergency and code only calls. It should be noted that access to other licensed operators (OLO) such as Mercury use two stage calls. The first stage is treated as a normal code only call by the TXE4 and the second stage is dependent on the receipt of dial tone from the OLO and the transmission of MF pulses from the calling customer to the point of interconnect of the OLO. 1> Service Address Codes... On calls to the DMSU or DJSU the TXE4 does not forward the leading "0". Until now the London DMSU's and DJSU's have used a locally agreed code for level 1 and 999 calls eg. 1199X for 999 or 1112X for 112 calls etc... With the advent of the of the National Code Change in 1995, misrouting would occur on new codes beginning with 011X and the existing codes used in London. This problem does not arise when level 1 or 999 traffic is routed via a DLE, however over the next few years these direct routes are likely to disappear and all calls will route via a DMSU or DJSU. The problem above can be overcome by using a unique service address code for TXE4 exchanges... When making a c7 code only call, the TXE4 can send up to five translation digits, or a service address code of eight digits. Non-director exchanges also have the option of sending 5 translation digits followed by the dialled digits. The service address code of eight digits sent are made up from a "service address" of five digits entered in the enhancement "operator code table", followed by 1XX. The code of 9998X has been reserved for national use. The value X will be in the range 0 to 8 and used as a routing or control digit to select a particular queue or destination. An X value of 9 has been reserved so that 099989 can be kept as a spare code at the DMSU (Preference???). Examples... CODE SERVICE ADDRESS DIGITS SENT 999 99984 99984199 100 99984 99984100 2> Provision of Service Address... As soon as a service address is entered in the enhancement then all C7 calls to that code will send an eight digit service address code instead of the translation digits. If a service address is being provided then it is necessary for all the destination digital exchanges (DMSU, DJSU or DLE) for that code to have a data build against the existing translation digits (up to five) as well as the eight service address code digits. If the destination digital (outgoing route number) is changing at the same time as the provision of the service address then care must be taken to change the translation and provide the service address in the correct order. Initially it is proposed that the new destination will support both the old translation digits as well as the eight SAC digits during the change over period. 3> Fraudulent Access... :) If for example access to 192 (directory enquiries) is given via the DMSU with a SAC of 99981 then a customer/phreak dialling 099981192 would be able to access 192 free of charge. This would also apply to any chargeable codes accessible via the level "0" route. To prevent this occuring BT have made sure that the 09998 code has been translated to give a NU tone. This is possible due to 09998 being a non-geographical code. Eg... a>In a Director Exchange... SEARCH DATA READOUT DATA J 8 + + 9 9 9 8 + 0 0 3 7 9 9 9 8 9 ^-. |___| |_______| | | | Origin Flag | SPARE CODE AT DMSU (+ for London,) | (maybe 2 elsewhere) DMSU ROUTE NUMBER In the above case if a customer dials 09998 the call will attempt to route to a spare code in the DMSU and will receive NU tone. b>In a Non-Director Exchange SEARCH DATA READOUT DATA J 8 1 + 9 9 9 8 + 9 8 0 9 6 9 3 4 1 ^-. |___| | | | `-TI=CPI Origin Flag | (+ for London,) | (maybe 2 elsewhere) DMSU ROUTE NUMBER The method above uses the CPI facility (TI = 3) to bar all calls to 09998 EXCEPT for calls from lines with a CPI COS (COS 2 = 7). No customer lines should be given a CPI class of service thus all callers to this code will receive NU tone. 4> 999/112 TRAPP Circuits... TRAPP circuits are used so that calls to a particular code are only given access to part of a route. These are generally used for numbers allocated to TV and radio phone in programmes. For the first junction in each 999 route the TRAPP route number will be used for 112 access and for 999 testing. For subsequent junctions on each route the TRAPP route number is used for 999 testing only. The facility is provided by giving two route numbers to one junction ie... two 36ms slots. Junction EN ------------- CG/FG Normal 999 Route number and EA | `---------- CG/FG TRAPP route number and same EA In London an attempt was made by BT to allocate the route numbers in a user friendly manner (for them or for us? haha, lamers!) For example, the BBC's phone in lines... 0181 - 811 primary cct1 821 alt.1 cct1 831 alt.2 cct1 812 " " 2 822 " " 2 832 " " 2 813 " " 3 823 " " 3 833 " " 3 816 " " 6 826 " " 6 836 " " 6 etc. 5> Routing Arrangements... I > 999 Routing Arrangement Part of the rollout of C7 signalling at London TXE4 exchanges has allowed a standardised routing arrangement to be used for 999 access. This standardising routing arrangement was designed to maintain the security of 999 calls and to provide secure access via the TS 16 route in the event of enhancement or C7 failure. The 999 Routing arrangement is as follows :- a> Primary, Dedictated DLE 999 route (C7 signalling) b> Alternative 1, Dedicated DJSU 999 route (C7 signalling) c> Alternative 2, Dedicated DLE 999 route (timeslot 16 signalling) II > 112 Routing Arrangement Code 112 was rolled out by BT in December 1992 in agreement with the request from the European Commission to provide a pan-European emergency access code. It has been agreed that this access code will run in parallel to the UKs own emergency access code of 999. For London TXE4 exchanges, access was initially provided on a shared route basis with the Dedicated DJSU 999 route. There have been several problems for BT regarding the introducion of this new code. Briefly, the choice of digits (112) has made no allowance for known digit insertion problems caused by spurious line conditions and cable failures. The result of such conditions cause the emergency operator to receive random surges of phantom or silent calls. It was for these reasons that code 112 was initially only allowed restricted access via the 999 Dedicated DJSU route. Had full access been given via all 999 routes the problems suffered through line faults would seriously affect or block normal 999 access. Restricting access for code 112 to one route only is vulnerable to failure through lack of resilience and security. In order to gain security and resilience but maintain limited access, code 112 went through a further routing change. In brief, TRAPP circuits ar used to allow 112 access over ONE 999 JUNCTION ON EACH 999 ROUTE. The 112 Routing arrangement is as follows :- a> 112 junction 1, access via TRAPP cct to the first junction on the Primary (Dedicated DLE) 999 route (C7 signalling). b> 112 junction 2, access via TRAPP cct to the first junction on the ALT 1 (Dedicated DJSU) 999 route (C7 signalling). c> 112 junction 3, access via TRAPP cct to the first junction on the ALT 2 (Dedicated DLE TS16) 999 route (TS16 signalling). 6> Introduction of Service Address for 999/112 in London... At present the translation digits sent to the OSSU host DLE on the primary route are different to the digits sent to the DJSU on the ALT 1 route. When changing to service addressing the same digits are sent on all C7 routes accessed by the same code ie. if 999 is service addressed with a code of 99981 then te digits sent on the primary (DLE) and the ALT 1 (DJSU) routes would both be 99981199. At present the DLE expects 999 for 999 calls and would be unable to distinguish this from 999811XX to be used on other codes. To overcome this and to ease the changing of TXE4 site data to coincide with the DLE and DJSU data the following chain of events is followed. Stage 1 > The DJSU will provide a databuild to support dual access for the existing translation digits and the service address digits. ie. CODE EXISTING TRANSLATION DIGITS SERVICE ADDRESS DIGITS 999 1199X 99981199 112 1112X 99981112 Stage 2 > The DLE will provide a databuild to support dual access for 998 and 999 to both route to 999 from the C7 route. The timeslot 16 is unaffected bt these changes. Stage 3 > The TXE4 exchanges will change their primary 999 translations (and duplicate) to send 998 instead of 999 on the primary route. At Non-Director exchanges this requires the use of J31/32 translations to send the translation digits of 998 instead of repeating the dialled digits of 999. Stage 4 > The DLE will provide a databuild to support dual access as follows :- CODE EXISTING TRANSLATION DIGITS SERVICE ADDRESS DIGITS 999 998 99981199 112 112 99981112 Stage 5 > The TXE4 exchanges will now provide service addressing on 112 and 999 and remove the translation digits from the primary and ALT.1 translations (and duplicates) for these codes. At Non-Director exchanges the J31 and J51 translation will change to allow the removal of the J32 and J52 threadings. The ALT.2 route translations will be unaffected by these changes. Stage 6 > the DLE and DJSU will now remove the databuild supporting the dual access ie. 998 and 112 at the DLE and 1199X and 1122X at the DJSU to be removed. - -- ----------- ----------------------------------------- ------------- -- - aNOtHEr qUAlitY rElEASe fROM tHE m.E.D, sTRAiGhT fROM tHE fiRE iNtO yOUR lAP! - -- ----------- ----------------------------------------- ------------- -- -