Indeed ISDN TE has gone through at least three generations of evolution in the past decade. ISDN Centrex has been available in parts of the United States since 1988. ISDN's acceptance in other countries has been far greater. Germany, for example, has a consumer-level mass ISDN market that greatly exceeds in size the entire United States ISDN market. This comes about in large part because Deutche Telekom has positioned ISDN favorably.
ISDN line ordering and provisioning is geared towards high volumes.