1. HDB3 Alan Mitford-Taylor

2. 2 What is the issue with HDB3 HDB3 systems can be adversely impacted by ADSL systems in same cable binder The IMP requires the separation of HDB3 and ADSL The draft STD requires Removal of HDB3, or Replacement of HDB3 as soon as reasonably practical, and reduced power on ADSL until removed. Chorus requires a process to remove HDB3 that reflects the need of end users for time to migrate to replacement services

3. 3 What is HDB3 HDB3 means high density bipolar of order 3 and it is a method of encoding data signals to ensure there are an equal number of positive and negative pulses. HDB3 provides several advantages over early systems No DC component to data signal enabled power feeding of repeaters Network synchronisation maintained Data errors easily detected.

4. 4 What is HDB3 used for HDB3 has been used since the late 1960’s as the signalling method for 2 Megabit/sec digital systems from exchange to exchange or exchange to end customer premise. These systems support Voice – ISDN Data - WDDS Interconnect - Megalink

5. 5 What is wrong with HDB3 Nothing is wrong with HDB3, it is still fit for purpose It can be adversely impacted by ADSL systems in same cable binder STD requires Separation of HDB3 and ADSL, or STD requires Replacement of HDB3 as soon as reasonably practical, and Reduced power on ADSL until removed.

6. 6 End Customer will be impacted by removal of HDB3 systems While there are many more ADSL circuits that the 15,864 HDB3 circuits, there can be many end users affected by one HDB3 link Need to upgrade communications equipment May need to upgrade entire systems including premise wiring and CPE (phones & terminals) Need to be able to choose their own timing and have plenty of notice Have to meet costs that are potentially unbudgeted and also earlier than expected

7. 7 How can we mitigate impact of HDB3 Chorus has designed pair selection process to avoid HDB3 binders until only choice All have opportunity to sell end users an upgraded system Where distance permits replace HDB3 span with alternative xDSL based systems

8. 8 Long term view of HDB3 Undertakings require progressive closure of legacy services based on HDB3 systems from December 2007 through to the end of 2009 HDB3 will still be required for interconnect and voice mux systems after 2009, but in much reduced numbers mainly in non-urban areas Work with Customers to manage removal of HDB3 systems where possible Sales opportunity for all to up sell end users