As well as any analogue phone lines you may use for your business phones, if you have other devices connected to your phone line, such as alarm systems, payment lines, CCTV etc you might need to upgrade them to make sure they're compatible with the new digital connection. If you're unsure about how a device in your business might be affected, it's recommended that you contact the equipment supplier or device manufacturer to find out whether it will remain functional on a digital phone line.

Find out more from the BT website.