A multiline is a group of telephone lines with one telephone number. The first line is known as the main exchange line, whilst the extra lines are known as auxiliary lines.

The additional line (or auxiliary line) is added to your main exchange telephone line so there’s no need for a new number which means no changes to advertising, marketing material, stationary, etc. Having an auxiliary line added to your existing PSTN (analogue) line means that if a call comes through to an engaged line, the call will simply be passed to the next available line.

There is no limit to how many auxiliary phone lines you can have attached to one telephone number. Multilines are generally connected to a telephone system.