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Getting started with ISDN30/30e | BT Business

Getting started with ISDN30/30e

Find all the information you need to get started with ISDN30/30e. 

How many channels can I have?

ISDN30/30e has no maximum limit unless the capacity of the exchange is exceeded. A site survey is performed for every new order. If ISDN30 isn’t enabled at an exchange, BT can enable it, though this is charged as an additional installation cost.

Although a single ISDN30/30e bearer supports up to 30 channels, you can have ISDN30/30e with as few as 8 channels activated. If you want to add channels to your circuit, you simply request that additional channels be activated. For more information on this, please contact ISDN30/30e sales on 0800 587 0436.


The process of using multiple lines to make calls is known as 'channel-bonding'; it’s one of the most useful features of the service. Combining two ISDN channels lets you access the internet at more than twice the speed of a standard analogue modem. Your computer's software controls this procedure, which is known as channel-bonding.

If you want to use channel-bonding you should check with your supplier that your software supports this function, and also that your ISP supports 128k internet access. When you connect at 128k you’re making the equivalent of two simultaneous calls over your ISDN line. Meaning that you’re accumulating two concurrent sets of call charges.


Point-to-point is the standard configuration of ISDN30/30e where the exchange expects one piece of equipment only to be attached to a circuit at any given time. If more than one item is connected, a conflict will occur.

Connecting existing office PCs directly to ISDN30/30e to access the internet

You can’t connect existing office PCs without the right equipment. Most Internet Service Providers (ISPs) will accept only connections from a Basic Rate Interface (BRI) line. ISDN30 is a Primary Rate Interface (PRI) line. You’ll need to contact your switch maintainer to find out if it’s possible to add a BRI card to your PBX/switch. This will enable you to access two 64k channels of ISDN.

Receiving incoming faxes on ISDN30/30e

You can receive incoming faxes as long as the equipment and software you’re using is compatible. Contact your supplier for further advice.

Video-conferencing on ISDN30/30e

ISDN30/30e can support voice or data calls, including digital video- conferencing. Calls can be made on multiple channels simultaneously which is known as ‘channel-bonding’. You can find more information on channel-bonding above in this article.

Video-conferencing equipment used with ISDN lines provide high-quality sound and pictures. Video-conferencing units may aggregate two or more 64k ISDN lines to provide the bandwidth needed for good image quality.

Both parties in a video-conferencing session need ISDN access and compatible equipment. Some packages allow you to connect several users in a video-conference meeting. This saves time and travel expenses.

Will my alarm system run over ISDN30/30e?

If your alarm system requires an analogue circuit you might still be able to connect to ISDN30/30e if you have a PBX/switch with PSTN inputs. But you’ll need to check with your alarm company that their system supports connection via digital switching equipment.

What maintenance and resilience options are available?

Maintenance options:

There are two packages available, each with different response times and reporting hours:

Package  Reporting Days  Reporting Hours  Response Time
Prompt Monday to Saturday  8 till 5 4 hours
Total 7 days a week 24 hours a day 4 hours

An upgrade to Total Care can be ordered through ISDN30/30e Sales, on 0800 587 0436.

Resilience options:

Your ISDN30/30e connection can be delivered in several different ways to make sure that in the unlikely event of a failure, such as a JCB damaging your line, service impact is kept to a minimum.

Standard connection and rental charges apply for standby lines served from the same exchange as your primary site. If you require the standby lines to be serviced via a different exchange, out of area charges will apply in addition to connection and rental charges.

1. Back in Business – Single Site

  • Calls are diverted to a BT Managed Call Centre.
  • Customer calls pre-allocated BT number to request service.
  • Suitable for customers with fewer than 30 channels.

2. Alternate Routing

ISDN30/30e can be routed via separate cables from the serving exchange. There are two options:

  • separate cables, same ducting
  • separate cables, separate ducting.

3. Diverse Routing

The service is provided via two different cables from two different serving exchanges. In the very unlikely event of a cable failure and a problem at the exchange, the chance of a complete loss of service is reduced. Separate DDI groups are served by the two exchanges.

4. Dual Parenting

The same DDI numbers are served from two different exchanges. This means that in the unlikely event of a problem with one of the exchanges, calls can still get through. Dual Parenting can be provided in one of two ways:

  • Option 1 uses two different exchanges and connects the ISDN 30 service via Diverse Routing.
  • Option 2 connects your site to the local exchange via two ISDN 30 bearers provided using the same duct and cabling. Once at that exchange, however, half the calls are diverted via the BT network to the next nearest exchange and alternative processor.

5. ISDN30/30e Site Assurance

Again, there are two possible options:

  • Option 1, 'Back in Business Multi-Site', uses Call Diversion for ISDN30 (DASS2) or Call Forwarding for ISDN30e services. Should a problem at your primary site occur, voice calls for ISDN30 (DASS2), and voice and data calls for ISDN30e, are diverted to a pre-arranged single number. On a request being received, the changeover to the standby site usually takes place within 30 minutes per bearer. You will be charged for the diverted leg of the call with this option.
  • Option 2 is delivered by providing a group of ISDN30 lines to your standby site. These lines are provided with a status of 'out of service'. If a problem occurs at your primary site, at your request, primary site lines are adjusted to 'out of service' mode and standby lines are brought into service. The back-up lines allow DDI, voice, and data calls for both ISDN30 (DASS2) and ISDN30e to be mapped across to your back-up site. 

High speed data transfer

Using high speed file transfer, you can send files directly over the ISDN network to another computer with ISDN access and compatible file-transfer software. This is particularly useful for large documents, graphics or video files. It is often quicker and cheaper than using a courier.

Remote access

Using ISDN30/30e, you can connect remote users to your central site server. This enables staff to work from satellite offices or their homes. The central site requires ISDN connectivity and ISDN-compatible equipment (typically a router) that allows remote users to dial-in.

Remote users need an ISDN line with a PCI card or Terminal Adapter (TA). When setting this up you should install a security system such as a firewall to prevent unauthorised access to your company's network.

LAN connection

You can use ISDN30/30e to link two or more Local Area Networks (LANs) to create a Wide Area Network (WAN). This allows employees working in different locations to access the same information. The link requires a router at each end to connect the LAN hubs to the ISDN line.

Intelligent Broadband On Demand

The speed of internet access via a LAN will depend on the amount of internet activity sharing the available bandwidth. Many routers offer Intelligent Bandwidth On Demand (IBOD). This is designed to optimise your internet connection while avoiding unnecessary call charges.

What voice applications can I use with ISDN30/30e?

You can connect high-quality digital phones to an ISDN circuit.

There is a wide range of PBX phone systems and switches compatible with ISDN. In addition to switchboard functionality, many PBXs offer functions such as call transfer, call pick-up, call hold, etc. A modern ISDN-compatible PBX is easy to use. Most are controlled by computer software.

These systems usually require expert installation and configuration. You should check that your supplier offers installation support.

ISDN30e is also compatible with Computer Telephony Integration (CTI), allowing you to see a caller's details before you answer the phone. This could, for example, enable your staff to check a caller's credit and buying history before engaging in a conversation.

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