Analogue Line Types


There are three types of PSTN line. Each form the basic traditional phone lines all customers will be familiar with. The differences between them are detailed below:

Residential PSTN

Known by Openreach as ‘Basic’ lines these are cheapest PSTN available and typically used in residential solutions. They come with Care Level 1 as standard which means that delivery and faults aren’t as quick as other types of lines, or those with higher care levels. These can support broadband.

Business PSTN

Business PSTN lines, known by Openreach as ‘Premium’ lines, don’t physically differ from a residential line, but they have a number of unique benefits including:

  1. They have Care Level 2.5 as standard, ensuring you get quicker responses from Openreach when you need them, and priority over Residential PSTN faults.
  2. Ability to have a line box installation or NTTP connection. A residential line will only present the option for a line box.
  3. You can have a business directory enquiries listing.

We are often asked whether it is imperative to install a business PSTN line for a business. The answer is very simple: If the installation address is a business premises (such as a shop or an office), then your best option is to order a business PSTN line. If however you are a small business, operating from a residential premises, you can choose to select a residential PSTN line, however you won’t necessarily benefit from features listed above.

Broadband can be installed on Business PSTN lines.

Multi-line PSTN

A multi-line allows you to connect multiple PSTN line boxes to one number. This can present a cheaper and more flexible solution to an ISDN2 or ISDN30. Incoming calls to a multi-line will ring the phone attached to the first socket. Should the line be in use, the second socket will ring and so forth. This line arrangement is best used in conjunction with a PBX phone system. In much the same way as Business lines, they have care level 2.5 as standard.

NOTE: It is not possible to install broadband on a PSTN Multi-line.


Digital System

This is when an ISDN2e line connects to a PBX. Signals from the network travel as far as the PBX which then, according to how it’s programmed, decides the onward routing. DDI’s can be set up with this configuration to point to internal extensions. This is the most popular choice of ISDN configuration.

Digital Standard

This is a configuration where one stand alone ISDN2e line connects straight to equipment. These are typically used for data applications owing to the inability to support line hunting or multiple channels beyond the initial 2.


ISDN30 lines have applications for handling large volumes of calls as well as combining them for high bandwidth applications such as video conferencing or the transfer of large files. The is a minimum number of 8 channels required and a maximum of 30 per bearer. An ISDN30 can support multiple bearers for solutions which require in-excess of 30 channels / simultaneous calls.