ISDN (ISDN 2 & ISDN 30) Moving office? Growing your staff? If you need more telephony capacity, whether more analogue lines or more ISDN lines, talk to us about your telephony services requirements. Intercity can make it happen quickly, seamlessly and cost effectively. ISDN enables businesses to bring together voice solutions combining both down a single line, enabling you to connect multiple devices to the line and make 2 calls or more at the same time. Why buy a Business Phone Line or ISDN from Intercity?