ISDN: Data Rates, Access Channels

ISDN stands for Integrated Services Digital Network. It was first introduced by NEC in Japan. There basic purpose was integration of traditionally different computer and communication (C&C) services into a single one. The integration basically means incorporation of three types of services:
Voice (telephone)
Data (internet)
Entertainment (TV)
The integration should be most comfortably and efficiently done in digital domain, so the switching, multiplexing, signaling and transmission, everything should be digital. It was first named integrated digital network (IDN), which received lukewarm response as only the enterprises, not the general public, realized the potential behind that acronym. Later on it was named ISDN which more clearly states the idea (of integrating different services) behind it.
INTERNET INCLUDES VOIP, TELEPHONY-OVER-IP, AND VIDEO-OVER-IP, BUT QOS WAS NOT MAINTAINED.
Later on, entertainment service providers started providing data service with cable modems. It has been very rare, though.
ISDN SERVICES
The key ISDN services, form the very beginning has been the voice service, although with many enhanced features. One ISDN feature is telephones with multiple buttons for instant call setup to arbitrary telephones anywhere in the world. Another feature is the display of caller’s telephone number, name and address during ringing. A more sophisticated version of this feature allows the telephone to be connected to a computer so that the caller’s database is displayed on the screen as the call comes in. other advanced voice services include call forwarding and conference calls worldwide. Advanced non-voice services are remote electricity meter reading, and on-line medical, burglar, and smoke alarms that automatically call the hospital, police, or the fire brigade, respectively, and give their addresses to speed up responses.
The cost of ISDN is accounted to the CPE interface and the service itself, so only the corporate users welcome it.