ISDN ISDN (integrated services digital network) is a development
from IDN (integrated digital network) that has performed the trans mission and switching of phone calls within digital exchanges and switches. It is a standard that has been around for a long time and but has only recently been gaining popularity. Introduced in the mid 1980s, its provision to the subscriber was dependent on digital ISDN compatible switches being in place plus sufficient bandwidth being available to support them. As a result, the introduction of ISDN services in many countries depended on the replacement of non compatible exchanges and switches and this has taken many years. It must also be said that the line tariffs and cost of adapter cards have slowed its introduction but this issue is also being addressed.