On a PSTN single line you can have a service called Call Sign. This gives you an extra number for that line, When that number is called the phone will ring with a different cadence. You can thus distinguish between incoming calls. Eg personal and business calls, or calls from specific people who have been given the extra number.
For more information, prices and contact details to order the service (or other calling features) please look at the Sales page.
BT Business Forum Moderator