Consult21 Information is subject to change and is for discussion purposes only. Any dates/timings are the current anticipated timescales and may be subject to change. I&M WG 1 Forward Looking Statements – Caution Advised Certain statements in this presentation are forward-looking and are made in reliance on the safe harbour provisions of the US Private Securities Litigation Reform Act of These statements include, without limitation, those concerning: BT's plans for transformation of its networks; benefits to customers of the 21CN programme; key milestones and expected timetable for delivery of 21CN; and the benefits in relation to, for example interconnect, convergence and broadband. Although BT believes that the expectations reflected in these forward-looking statements are reasonable, it can give no assurance that these expectations will prove to have been correct. Because these statements involve risks and uncertainties, actual outcomes may differ materially from those expressed or implied by these forward-looking statements. Factors that could cause differences between actual outcomes and those implied by the forward-looking statements include, but are not limited to: material adverse changes in economic and financial markets conditions in the markets served by BT; supplier arrangements; future regulatory actions and conditions in BTs operating areas; technological innovations; developments in the convergence of technologies and the anticipated benefits and advantages of new technologies, products and services, including broadband, not being realised.

Consult21 Information is subject to change and is for discussion purposes only. Any dates/timings are the current anticipated timescales and may be subject to change. I&M WG 2 PSTN Voice Migration Update This presentation includes: 1.PSTN tones update (slides 3-7) 2.BTs Existing Network Architecture & PSTN Voice Migration (slides 8 – 11)

Consult21 Information is subject to change and is for discussion purposes only. Any dates/timings are the current anticipated timescales and may be subject to change. I&M WG 3 TONES, RINGING & ANNOUNCEMENTS AS EMPLOYED IN THE BT NETWORK John Barton The purpose of the following presentation is to share with Communication Providers: Defined specifications for tones, ringing and announcements within BTNR1080 Tone variations and possible impact through network transformation Identified PSTN & 21CN tone differences

Consult21 Information is subject to change and is for discussion purposes only. Any dates/timings are the current anticipated timescales and may be subject to change. I&M WG 4 Tones, Ringing & Announcements & network transformation BT has defined its current (& 21CN) Tones, Ringing & Announcement specifications within BT Network Requirements (BTNR) Number CN selected vendors have been requested to meet the BTNR No1080 specification Providing Vendors meet BTNR 1080 requirements there should be no significant changes as associated with network transformation Work is in progress with BTs 21CN Vendors to demonstrate their equipments capability of complying with the BTNR 1080 specification

Consult21 Information is subject to change and is for discussion purposes only. Any dates/timings are the current anticipated timescales and may be subject to change. I&M WG 5 PSTN Tone variations & the possible impact of network transformation In the PSTN, two Vendors have supplied the Tone, Ringing & Announcement infrastructure BTNR 1080 defines the following tolerances for tones: frequency ± 2 Hz, cadence ± 10 ms & Power level ± 2 dB BTNR 1080 specifications have been met by the both manufacturers however minor differences exist, as a consequence of the permitted tolerances With the 21CN, BT has selected two (non PSTN) vendors for the delivery of MSANs - from where most tones are delivered Minor tone changes as associated with network transformation are possible.. Vendor differences result from BTNR tone tolerances, however these tone differences should not be discernable by the average End Users hearing. Note that tonal differences already exist in the PSTN….

Consult21 Information is subject to change and is for discussion purposes only. Any dates/timings are the current anticipated timescales and may be subject to change. I&M WG 6 Identified PSTN & 21CN Tone differences (1) Special Dial Tone will change co-incident with 21CN migration. Special Dial Tone is used in place of Dial tone in order to advise End Users that either a) Supplementary Services have been invoked (e.g. Call Diversion) or b) as Message Waiting Indication (e.g. with Call Minder / BT Answer) –New 21CN Specification - 350Hz frequency, Cadence 0.75s On, 0.75s Off + 440Hz frequency, continuous –Previous Specification– 350Hz+440Hz frequencies, Cadence 0.75s On & Off

Consult21 Information is subject to change and is for discussion purposes only. Any dates/timings are the current anticipated timescales and may be subject to change. I&M WG 7 Identified PSTN & 21CN Tone differences (2) Howler Tone – This tone provides an audible indication to attract the attention of a customer, whose telephone has been left in the 'off-hook' state The howler tone is of the frequency swept type with the tone varying in the range 800 Hz to 3.2 kHz, at a sweep rate of 1 Hz with a peak power of +20 dBm Based on MSAN Vendor information, it is currently believed that: the 21CN Howler variant may employ both a lower power level and different frequencies

Consult21 Information is subject to change and is for discussion purposes only. Any dates/timings are the current anticipated timescales and may be subject to change. I&M WG 8 21CN Migration of PSTN Voice Services Phill Couldrey The purpose of this presentation is to articulate to Communication Providers: 1.The relationship between the Digital Local Exchange (DLE) and Serving Exchange (SVX), emphasising the fact that the DLE is just one entity in the SVX supporting Voice Service, the DSLAM is an entirely separate entity for Broadband Service and Data Mux for Private Circuits. 2.Service migration how we will avoid impacting other non-voice services 3.Where the DLE fits into the PSTN network

Consult21 Information is subject to change and is for discussion purposes only. Any dates/timings are the current anticipated timescales and may be subject to change. I&M WG 9 Existing Network: BTs DLE & Serving Exchange Areas 1.The BT circuit switched voice network is based around System X and AXE10 digital local exchanges (DLE). (For simplicity I only use System X examples from now on.) 2.A DLE comprises a processor and all that processors remote concentrator centres (RCC). 3.Every processor has one or more RCC and each RCC contains one or more remote concentrator unit (RCU). 4.Each RCC has its own unique range of telephone directory numbers. 5.End Customers including Wholesale Line Rental customers are grouped into serving exchange (SVX) areas comprising the access network from the customer to the exchange building housing the RCC. 6.In any SVX area there will be one or more RCC, each controlled by its own processor. This provides resilience of service as capacity grows. 7.Changes to a DLE only affect the customers served by the DLE and not any customers connected to other DLE in the same SVX (if any). BTs VIEW OF VOICE

Consult21 Information is subject to change and is for discussion purposes only. Any dates/timings are the current anticipated timescales and may be subject to change. I&M WG 10 Existing Network: BTs DLE & Serving Exchange Areas 1.BT offers a wide range of analogue and digital non-voice services. 2.These services are supported by a number of disparate platforms e.g. xDSL, Megastream, SDH, LLU, etc. 3.Non-voice services represent a small percentage of the total services in any one SVX. 4.Any customer in the SVX is connected to any of the platforms as required. BTs VIEW OF NON-VOICE

Consult21 Information is subject to change and is for discussion purposes only. Any dates/timings are the current anticipated timescales and may be subject to change. I&M WG 11 Existing Network: BTs DLE & Serving Exchange Areas MDF Access Network to End Customers RCU 1 RCU 2 RCU 3 RCC a Processor A (co-located) Processor B (remote) RCC b RCU 1 NGS Non-voice platforms z xDSLSDH LLU Various back-haul systems To other RCC DLE A DLE B SVX

Consult21 Information is subject to change and is for discussion purposes only. Any dates/timings are the current anticipated timescales and may be subject to change. I&M WG 12 ATM B-RAS DSLAM Call Server Ethernet B-RAS Ethernet Backhaul * MSAN PSTN DLE * * Retained Legacy Concentrator Retained Legacy DSLAM EvoTAM Acterna TH Teradyne TH 21C A/TH 21C T/TH TE plug Existing FTAM or ETAM if fitted PSTN Voice Migration independent of non- voice services - example BB Migration PSTN Concentrator

Consult21 Information is subject to change and is for discussion purposes only. Any dates/timings are the current anticipated timescales and may be subject to change. I&M WG 13 In Summary BT can migrate PSTN Voice Services without affecting or impacting the non voice services