ISDN is not only faster than a traditional line with an analog modem, but it also has several capabilities not feasible with standard lines and modems. Yet, you can still place and receive voice calls to people that do not have ISDN, and in some instances still transmit data.
128 Kilobits per Second For Data or Video Transmission
ISDN transmits data up to 4 times faster than a 28.8 modem. If you are using a 14.4 modem, ISDN will be 8 times faster. These speeds are not achievable with a traditional modem.
Advanced Call Management and Video Conferencing
ISDN has capabilities not feasible with an analog line, such as the capacity for high speed data or video transmission, advanced call routing and management techniques. Video-conferencing is not feasible over a traditional line. Advanced call management is not possible with a traditional line.
2 Channels Two Communication Activities Simultaneously (Voice and Data)
ISDN has two primary channels or paths used for communication allowing you to do any two communication tasks simultaneously, such as data transmission and voice calls, or fax and data, or voice and fax. A traditional line can only perform one communication at a time. It would take two traditional lines to perform two tasks simultaneously.
Caller ID, Call Hold, and Call Waiting
ISDN comes configured with capabilities similar to some of the popular features offered by BellSouth. A traditional modem line does not come with these or any other services.