Channel Line Up

Set Top Box’s

ntl’s original franchise area, commonly known as ‘pure’ or Langely due to the location of the main headend was one of the major networks ntl had operated. Originally launched in March 2000, it was designed to compete with both Ondigital and Sky digital, and with upcoming IPTV services such as Homechoice. Unlike Telewest or the then Cable&Wireless, ntl designed their network differently.

The main common differentiation between the networks was the return path used for the TV service. C/W used DOCSIS (Data Over Cable System Interface Specification) for the Stb return path, this is what the STB used to communicate with the headend, which was going to be pivotal when using interactive and video on demand services. Ntl however elected to use DAVIC (Digital Audio Video Interactive Council) for its return path technology, which is entirely different in implementation and concept.

Generation A
Pace Di4001-1

DAVIC was first used in the US by Scientific Atlanta, and was designed to be used as a return path medium to give cable networks an advantage over satellite and terrestrial platforms, since these platforms do not have a native return path medium and require use of a telephone connection and a modem inside the STB, commonly a dial up modem. This means if a user wants to connect to enhanced interactive TV, they are limited by the bandwidth of a dial up modem, whereas capable can take full advantage of the bandwidth provided by DAVIC. Because DAVIC was becoming standard in the US, it made scene for ntl to adopt it for their UK and Ireland cable networks, and along with DAVIC ha also planned to adopt POWERTV for the STB middleware, which was developed by Scientific Atlanta.

A limitation for DAVIC was unlike DOCSIS it was not suite for PC broadband connections, and compared to DOCSIS could not provide enough bandwidth for future internet use. This is because DAVIC uses a combination of QAM and QPSK which results in a more robust signal, whereas DOCSIS supports up to 256QAM which provided more bandwidth but a less robust signal. This was important as since ntl had inherit many networks that were built very differently due to the requirements and budget of the legacy cable networks, some network had signal strength and noise issues with certain QAM levels. DAVIC would eventfully be incorporated into the DVB-RC specification, and continues to be used by Scientific Atlanta.

The original middleware planned to be used was PowerTV which wad been recently acquired by Scientific Atlanta, however the service actually launched with no middleware. The guide software was an actual program create by Pace and written in C and functioned as a basic TV guide. Ntl later announced it had entered an agreement with Liberate to license their navigator platform for their interactive services. This was done around the same time ntl had acquired cable&wireless, who had already deployed services using the Liberate TV Navigator middleware, and ntl wanted to unify the platforms at some point in the future. This was to allow interactive services from the Bromley platform (Cable&Wireless) to be carried over with little to no changes in code.

Aside from the differences in return path technology outlined above, both platforms (and Telewest) used DVB-C for TV broadcast, MPEG2 codec saw used for both TV and radio and the condition access system used was Nagravision. Despite both using liberate middleware, the Langely platform sued a different EPG than the Bromley platform, this was because although they both used DVB-C, the implementations of how the EPG guide data operated was different, with Langely using the DAVIC modem to deliver the EPG listings using multicast. Another major difference was the remote control the system system, with Langely using a standard IR command set, and Bromley using the IRDA system.

This would be constant issue for ntl throughout until 2004, as Langely customers would not be able to access interactive and TV email services due to the differences and issues unifying the platforms. Both platforms also had different channel numbers, with BBC1 being on channel 1 for lengthy, and channels would be grouped by package. Whilst Bromley channel numbers would start on 101 and would be grouped by genre, this remained until the Virgin Media genre.


Customer Release 3 was supposed to the software that introduced interactive to the Langely platform, and to be a major step forward in unifying the platforms. In addition, the guide interface was revamped and used a blue colour scheme that replaced the previous purple TV guides.

ntl had planned for CR3 to replace and combine the two platforms, and to offer a consistent interactive experience and EPG functionality. There were several differences between the two platforms;

ntl CR3 Guide

The DVB-SI, or System Information is the data that is sent on each of the transport streams )channels) that describes the network, channels and current events to the box. Currently this is different for both Langely and Bromley, with the latter using a DVB compliant version. Therefore it was decided that the CWC SI would be the default format used for both networks. The Langely SI format was designed by Nagravision, who are also responsible for the condition access system. This accounts for why there are differences in signal acquisition, ie the Langely boxes are capable of finding and setting their local Network ID, whereas Bromley (and Telewest) boxes have this fixed into the boxes EEPROM and cannot be modified by the end user, only via ntl/Virgin or through Digibug.

DVB-SI Information

NTL Migration Plan

The other major difference was the return path used, with Langely using the DAVIC or DVB-RC protocol instead of DOCSIS, which explains why Langely areas could not support broadband though the STB.

ntl CR3 guide that was meant to unify both platforms

The original STB deployed was the Pace Di4001, which undertook several revisions that removed the second card slot, IEEE1284 and RS232 were removed in favour of a single USB port and a change in STB chip with the Hitachi SH3 being replaced with an Conextant ARM SOC.

The Pace Di4010 was the replacement for the Di4001 and was designed to be used on both Langely and Bromley networks since its cable modem is capable of using either DOCSIS or DAVIC, allowing the STB to be used in either area depending on the software configuration, and for DOCSIS to be used in Langely area for the provision of using the STB for broadband internet. The later Samsung set top boxes also follow this design and can be used interchangeably.

Aborted PVR

Whilst Telewest was preparing to launch the TV Drive, ntl had also licensed a PVR from Scientific Atlanta in order to compete with Sky+ and Freeview PVR’s. This was deeply similar to the 8300DVB being designed for Telewest but ntl opted to use an MPEG4 decoder rather than the MPEG2 used in the Telewest box, in preparation of launch for high definition services. After ntl and Telewest had merged, the PVR was scrapped in favour of using the Telewest existing TV Drive DVR.


ntl also operated a cable network in Ireland, now known as UPC Ireland/ Virgin Media Ireland. This network was largely similar to ntl Langely with its use of DAVIC and DVB. However some areas of Ireland use MMDS (Multipoint distribution system), which used to deliver cable tv programming over rural networks using the 3 – 4 ghz band. For this a special antenna is use along with a baseband converter to allow the set top box to be used, along with a wireless DOCSIS cable modem. The same Pace Di4001 box was used for the Ireland service, but was later replace by the Di300, which was a cut own version that lacked the internal cable modem, with a dial up modem serving as its replacement, and only having a single smart-card slot and a single SCART socket. Ntl later sold the Ireland division to Liberty Media who then rebranded the service to UPC Ireland, in line with its other European branding.

manufacturermodelhardware typeramflashComments
PaceDi400108MB8MBS-Video over Scart, no RGB, dual card slots, internal bypass, Audio out
Di400118MB8MBS-Video over Scart,dual card slots, internal bypass, Audio out
Di40012a16MB4MBRGB over Scart, EPG runs from Ramdisk, internal bypass, Audio out
Di400138MB8MBRGB over Scart, internal bypass, Audio out, No Ethernet, No USB
Di40012b16MB4MBNo Ethernet or USB, EPG runs from Ramdisk, support external combiner, No Audio out
Di300n/a8MBIreland only, Single Scart, No audio out, V32 modem return path

32MB8MBSupports both DOCSIS and DAVIC, EPG runs from Ramdisk, inter combiner, No Audio out
8MBBased on Di4010, No Audio out

64MB8MBOptical audio out

Further STB Info

How to Identify Di4001 Revision

Looking at Pace Di4001NC

RF Bypass/Combiner

The RF out on early NTL STB’s is different compared to other cable providers, typically there is an RF in which is connected to the cable network and an RF out which goes to the customers TV/VCR. This was to emulate the RF configuration of analogue set top boxes where analogue channels would be passed through the RF, allowing the main terrestrial channels to be delivered over cable, in addition to some cable channels. Later set top box revisions removed this as NTL was planning to cease analogue transmissions on their network. If a customer wanted to use their antenna instead (if they had a DVB IDTV) a combined would be sued to combine the RF out channel from their STB with the antenna feed. NTL would also provide a bypass module for STB’s without an internal bypass to allow them to receive analogue cable channels through their TV due to legacy agreements set in by predecessor cable companies. This contrasts with how Telewest and Sky STB’s work where the RF in is connected to an aerial and the STB inserts it’s own RF signal onto a vacant channel.

Pace Di4001-3

Software Version History

3.28March 2000basic EPG and browse functionality basic reminder system composite-only output
3.32Jul 00
improved EPG data caching support for widescreen display option
support for S-Video/RGB output reminder management screen auto-tune reminders
3.34Aug 00improved return path re-connection
3.36Oct 00widescreen TV display fixes, Selected regions only
3.37Nov 00improved SI processing, Selected regions only
4.05Sept 00first interactive version TV email, selected interactive sites, Selected regions only
4.06Oct 00as 3.36, widescreen TV display fixes, Selected regions only
4.07Nov 00as 3.37, improved SI processing, Selected regions only
5.13March 2001interactive link available by pressing red while watching TV EPG remodelled new colour scheme page up/down to jump channels in 100s in browse functionality included for ntl Ireland subtitles support enabled, All Regions
5.14Open internet access. Revision A boxes only
5.16As 5.14, open internet access. Revision B boxes only
5.20new ntl corporate colour scheme volume controls favourites feature channel locking via PIN remodelled EPG enhanced TV widescreen switching fixes improved return-path connectivity improved reminder facility
Software update: On demand menu will reduce if there are no near-video-on-demand services available Software update: Help edited to contain details on Ireland functionality Software update: Purchasing procedure of near-video-on-demand events improved. Software update: Where radio channels are present, listings for these can be obtained from guide. Software update: STB ID split into 3, space separated, blocks of 4 digits when displayed to viewer. Bug fix: When copy protect has been implemented on a specific event and the following event does not require copy protection it was not disabled. This has now been fixed. Bug fix: In program list view when no events are available, ‘no information’ is displayed Bug fix: EPG was locking up when there were no normal channel entitlements but NVOD channels were available; this is fixed. Bug fix: Volume icon flashed on and off on audio channels – fixed. Bug fix: Events that have not yet started can be purchased.
5.26Bug fix: Programme listview titles corrected. Bug fix: Auto tune reminders now work with audio channels. Bug fix: Buy reminders are triggered when the buy window opens, not when the event starts.
STB Code Base: Source library for di4010 and di4001 merged – EPG can be built for either STB with using a build option. Software update: Error text changed, as specified by ntl. Software update: Browse re-structured so that viewer can browse with later times selected. Software update: ‘i’ keyboard button will give more info when this option is available. Software update: Minor changes to some guidance text. Software update: Programme listview page down functionality is now only enacted when there are more than 7 channels in the list. Bug fix: Fixes implemented to problems that occur when an access change notification is received when the STB is tuned or tuning to a purchased non-near-video-on-demand PPV event. Bug fix: When pressing ‘browse’ from within the guide or EPG area, the viewer is now returned to the current channel with the browse bar displayed. Bug fix: Multiple consecutive attempts to buy the same event ignored, preventing STB from crashing.
Bug fix: Pay Per View events now tune to the event when the purchase is made, and do not tune away randomly later.
The bug, introduced in version 5.28, whereby the STB would lock-up when a new NIT or SDT is received, while the STB is on an unpurchased near-video-on-demand channel not in preview, is fixed.
Fix: Video freezing is now fixed. Fix: Video blanking is now fixed. Fix: Cable modem fixes. Fix: Widescreen switching code fixed.
Contains measures to make Langley SI (System Information) more compatible with Bromley SI Enables Pace Di4001 set-top-boxes to receive standard teletext
P1.3.1.P0.CR3.CR3 for Pace Di4001
Release dates are not final

Ntl TV Internet

Acer NC-150 Cyber TV Internet
NTL Internet TV STB

Before it’s digital TV platform ntl had launched a TV Internet service, which allowed customers to access the (walled garden) internet through an STB. The service uses the Acer NC-150 set top box, which is NOT a DVB-C decoder, this could not receive digital tv signals, or scrambled analogue cable signals either, to a cable TV subscriber would need two boxes. This meant the TV internet box was not reliant on a cable feed since it used a 56k dial up modem and could be used on a BT line. Further information about this service:

DigitalSpy thread

ntl announcement (requires an account to read)

ntl announcement

DigitalSpy article about the service with screenshots#

ntl ditches TV internet

Acer CyberTV announcement

More Information – Former developer who ported PowerTV to the Pace STB for Ntl

ntl Microsoft TV announcement – never materialized since ntl went with Liberate

Liberate Technologies, Customers (archive.org) – ntl announcement