In 2015, BT announced that ISDN, the Integrated Services Digital Network first created in 1988 as Britain’s digital network for carrying sound and data, will be phased out by 2025. This may sound like drastic news to companies accustomed to using ISDN, but it has been a long time coming and is being phased out carefully – and there is a chance that, for some users, the deadline will be extended. The other non-internet network BT maintains, the analogue Public Switched Telephone Network (PSTN), will be gone by this time, too.…