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. 1 Mass Migration Methodology: Ray Lewis Queries to

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. 2 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 BT’s 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. 3 This presentation should be viewed in conjunction with the PSTNMass Migration Methodology Presentation presented at the IMWG on 15/11/05 by Alan Cameron (ref: SLOT 6 slides16 –23) This presentation is designed to inform Communication Providers of: 1.the migration activities which will be undertaken by BT including:  Pre-Transfer activities (identified as “Configure & Verify phase)  On the night Transfer activities  Post Transfer activities (identified as “Monitor” phase) 2.the impacts on End Customers of mass migration for PSTN VOICE SERVICES

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. 4 E-side MDF Pre-Transfer Pre-Transfer Activities Install, configure, cable & commission MSAN, 21CN Test Access Matrix (TAM), Test Heads & Comms Cable 21CN TAM to MDF & fit Transfer Connectivity Point (TCP) modules on E-side blocks TCP module installation checks 21CN Call Server & MSAN data build PSTN pre-transfer checks 21CN TAM PSTN CONC Customer lines OVPOVP OVPOVP OVPOVP Test Head POTS MSAN MDF D E 21CN TH PSTN DLE 21CN 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. 5 Pre-Transfer Activities - Detail TCP installation  Install & Commission phase incorporates a 100% end to end test of all 21CN equipment.  Pre & Post TCP installation checks ( BAU / Non-intrusive)  5 pair module = Target 30 seconds customer outage  5 pair module includes Over Voltage Protection  Trials: 100 pair block = minute TCP installation PSTN Pre-Transfer Tests  Check connection from 21CN TAM to TCP (Existing line) Business as Usual test / Non-intrusive  Check Pre-build MSAN services Non-intrusive test Activity Freeze before Transfer  Aiming for maximum 12 hours

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. 6 E-side MDF Transfer in progress Transfer Activities Command & Control confirm transfer “Go/No Go” Disconnect PSTN concentrator & Switch 21CN TAM Sync with changeover from DLE to Call Server 21CN TAM PSTN CONC Customer lines OVPOVP OVPOVP OVPOVP MDF D E MSAN 21CN T/TH Test Head POTS PSTN DLE 21CN 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. 7 Transfer Activities – detail Transfers will happen overnight in periods of low network activity but may be scheduled for any night of the week Transfer Go / No Go Decision  Various defined decision points along Transfer timeline  Final decision approximately 10pm Calls in Progress  Calls in progress will be lost, however, special measures to prevent disruption of 999 calls will be implemented PSTN Disconnection  Number of options under consideration Testing to determine most suitable to minimise service outages 21CN TAM Switching  21CN TAM suite (Max lines) = <10 seconds (Outgoing calls)  PSTN to 21CN re-routing = minutes (Incoming calls)  Alignment of both to minimise total service outage

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. 8 Transfer Activities - End User Experience Outgoing calls  Short break in dial tone during 21CN TAM switch  No service interruption announcement during switch Incoming Calls  Precise detail of service capability will become known upon completion of transfer engineering end to end trials phase.  Incoming call capability will be dependant upon size of number range and customer position within it. For those at the front of the number range restoration of service capability will be instant, for those further along the range, the duration will be longer.  A range of options are being considered as part of the transfer engineering solution to improve these timings.  Principle is to achieve the shortest service capability interruption possible Dial Tone  There will be no perceptible change in the dial tone heard by the end user once transfer has been completed.

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. 9 E-side MDF Post Transfer Post Transfer Activities Switch from PSTN Test Access to 21CN TAM Test Access Post transfer checks Monitor network for fallback period Decommission Redundant Equipment Hand-over to Operations 21CN TAM PSTN CONC Customer lines OVPOVP OVPOVP OVPOVP MDF D E MSAN Test Head POTS 21CN T/TH 21CN Voice PSTN DLE

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. 10 Post Transfer Activities - detail Post Transfer Checks  PSTN disconnection tests (Every Line)  MSAN connection (Non-intrusive) tests Review & Monitoring  Assess network performance against Fallback criteria (eg on the night test results / % faults)  7 day monitoring period Fault Reporting  Special measures will be in place for fault reporting for 7 day period.  Additional resource available to deal with any reports