Traditionally, multiple BT style analogue lines were the accepted method of delivering volumes of telephony traffic to standard business telephone systems.
Whereas this approach has in the past provided the required service, it typically results in lots of individual single telephone line wires coming into your building with each line then having to be independently cabled into your telephone system.
Compared to modern day digital ISDN lines (which deliver many lines down a single cable), traditional analogue lines can potentially offer a lower call quality, they can be difficult to manage when changing telephone systems and they are not as simple to expand. For these reasons, Your Telecoms Expert recommend that businesses changing or upgrading their phone systems, or moving premises, consider upgrading their lines to digital ISDN.
Although analogue lines have been superceeded by digital ISDN lines for business telephone system connectivity, they are still useful for connecting alarm systems, credit card terminals, franking machines and as a pre-requsite onto which standard ADSL broadband can be enabled.