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Important price changes
We're changing some of our prices from 1st April 2023. Find out what's changing by visiting bt.com/pricechange2023.
Reliable connections for voice and data
Integrated Services Digital Network (ISDN) is a high-performance service that delivers broadcast-quality voice and continuous, extremely reliable data transmission.
Continuous data transmission makes it ideal for use with EPOS machines and intelligent tills in shops. And that makes it especially useful in areas with patchy broadband coverage.

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ISDN2
For small businesses that can’t afford any breaks in data transmission. With ISDN2e System you can connect to a small switch (like Avaya IP office) with up to 60 channels. Channels are sold in pairs and can be bonded to increase bandwidth for things like reliable video conferencing.

ISDN30
For large businesses that need high-quality video conferencing, consistent transfer of large data files, or that operate call centres. Customers get an unlimited number of channels (sold singularly) and can also bond channels to increase bandwidth. ISDN30 supports WAN to link two or more sites.
Included as standard
We will aim to fix your phone line fault by the end of the next working day.
You can report faults 24/7/365 online or by phone:
call - 0800 800 154
But you may not need to contact us at all: our comprehensive set of FAQs and help articles on our website, plus help from other customers on our support forums, should answer most questions.
Optional extras
Protection against both cable and local exchange failure.
- We provide your ISDN over 2 different routes
- Different cables, ducts (where available), and building entry points
- Routing from 2 exchanges to your premises
If your site has been compromised, we’ll divert all your incoming calls to a single pre-arranged number.
ISDN30e channels duplicated at a standby site that we activate when you can’t use your main site.
We connect your site to 2 exchanges with the same number range across both exchanges.
So if one exchange fails, you’ll still get your incoming calls delivered from the second exchange.
If you’d like to add direct dial in numbers to your lines you can upgrade from £4.81 per channel per month (ex VAT)
.
2 options for more rapid fault fixes.
Total care
We will aim to fix any faults within 24 hours of you telling us about the fault (including weekends and public holidays).
Costs
ISDN2 and ISDN2e System: £6.49 a month extra for each pair of channels (ex VAT)
ISDN30e: £4.14 a month extra (ex VAT) for each channel
Critical care
We will aim to fix any faults within 6 hours of you telling us about the fault (including weekends and public holidays).
Costs
ISDN2 and ISDN2e System: £8.70 a month extra for each pair of channels (ex VAT)
ISDN30e: £5.95 a month extra for each channel (ex VAT)
Why BT Business?
Unlimited calls
Unlimited UK calls for just £12 a month
Over 900k customers
More UK businesses trust us with their communications
Round-the-clock support
24/7 online fault reporting and service status
Techie stuff
Technical details about ISDN2.
- Internet connection speed on each channel is 64kbps, which you can combine for faster transmission
- If you connect devices directly to the ISDN circuit, you can have up to 9 additional MSN (Multi-Subscriber Numbering) numbers
Technical details about ISDN2e System.
- If you connect devices directly to the ISDN circuit, you can have up to 9 additional MSN (Multi-Subscriber Numbering) numbers
- Internet connection speed on each channel is 64kbps, which you can combine for faster transmission
- Bond channels together for faster transmission for high-quality video conferencing and transferring large data files
- If you use a switch (PBX), you can have an unlimited number of DDI numbers (extra charges apply)
Technical details about ISDN30
- Each bearer carries 30 64kbps channels
- Bond channels together for faster transmission for high-quality video conferencing and transferring large data files
- If you use a switch (PBX), you can have an unlimited number of DDI numbers (extra charges apply)
- You can create a Wide Area Network (WAN) by linking 2 or more Local Area Networks (LAN) so you can link multiple sites together
- 2 configurations available: ETSI and DASS
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