Internet: Hardware Student Papers: Bartholomew - California Western
Internet: Hardware Student Papers: Bartholomew

The Case of the Disappearing Technology: An ISDN Mystery

by Diane L. Bartholomew

      ISDN is an acronym for integrated services digital network.  Originally, AT&T developed ISDN  to lessen the expense and increase the efficient transmission of analog, or voice signals, over copper telephone wires. Today, ISDN is a method of converting audio, video, and data to digital signals, and simultaneously sending those digital signals over telephone lines.

How Does ISDN Work?

     ISDN allows for utilization of multiple devices and applications simultaneously, unlike existing telephone service.  In a typical home, there are multiple telephone jacks, but only one telephone line.  Thus, a home with a PC, modem, telephone, and fax can only use one device at a time, unless multiple phone lines are installed.  With ISDN, all these devices can be run through the same line, and be used simultaneously.

     In addition to this multi-tasking ability, ISDN can carry more data at faster speeds than the fastest available modems.  ISDN service is provided by telephone companies through its lines on a Basic Rate Interface (“BRI”).  BRI widens the bandwidth of existing copper wire by dividing it into three logical channels. Two “B” (or bearer) channels move digital voice, video, sound, and data at 64Kbps.  The B channels can also be combined to move information at 128Kbps.  (The B channels can transmit even greater amounts of compressed data.  The other “D” (or data) channel carries data at 16Kbps. The D channel sends information to the telephone company’s switches on where to send the B channel data.

Who is Using ISDN?

     ISDN is becoming a popular business and media tool.  Presently, ISDN is most useful to networked businesses.  ISDN can be used for videoconferencing, which is ideal for joint collaboration on projects among widely dispersed individuals.  ISDN can also quickly transfer huge data files can reduce employee down-time during the wait, and can increase overall savings by reducing travel expenses and cutting project completion time.   

      One radio station uses ISDN to transmit new songs simultaneously to its affiliates.  Using ISDN means they no longer have to dub multiple tapes in 24-hour periods and then overnight the tapes to its affiliates.  ISDN completes a 24-hour job in minutes.  In addition to radio, ISDN offers benefits to television.  A Los Angeles station is using ISDN to transmit a full-motion video to the internet.  In order to receive the full motion video, internet users will need a two-way ISDN line.  If the broadcast is successful, broadcasters will not have to rely solely on cable to carry their programming.  If, in the future, cable refuses to carry network programming, the networks or broadcasters will be free to offer services over the internet via ISDN. 

       ISDN's primary benefit to internet users is its ability to quickly transfer huge graphics and data files.   Any PC user can also benefit from ISDN's multi-tasking capabilities.

Who Are the Major Players?

     Pacific Bell actively promotes ISDN service and has a large California constituency.  According to Pacific Bell, it has more than 46,000 customers using ISDN.  On the other hand, NYNEX in Rhode Island has only 19,000 ISDN lines reaching only about 150-200 homes.  Pacific Bell offers rates attractive to home users, while NYNEX prices are beyond the typical home users' reach.  However, Pacific Bell has filed a proposal with the CPUC to increase its ISDN tariffs.

     Continental Cablevision is conducting a large-scale test of its new cable modems, which are designed to provide a service faster than ISDN to the internet by high-capacity TV cables plugged into a personal computer.  Test participants highly rated the cable modem speed claiming there is "no dialing, [it's] always connected, and it's astronomically faster."  However, Contintinal's cable technology can only transmit one-way signals downstream to residences from the cable company.  ISDN, on the other hand, can sends signals both up and downstream, which is needed for two-way video transmission. Unfortunately for telephone companies,  Motorola Company claims it has a cable modem that offers speeds of up to 10 Mbps downstream and 768 Kpbs upstream, thereby creating interactivity.  ISDN cannot match these speeds. 

     One research company predicts: (1) ISDN prices will not be able to compete with cable's suggested price points;  (2) telephone companies' pricing will hurt adoption of ISDN; and (3) that online subscriber accounts via cable will match ISDN at 7 million by the year 2000. Clearly, the two major players are poised to battle for the high-speed data transmission market.  Speed is the key, but it may be the two-way capabilities that decides who will unlock the competitive door to success. 

      In addition to cable competition, telephone companies have another impediment standing in the way of ISDN's success: the Federal Communications Commission ("FCC").  In January, 1995, the FCC announced that phone companies had to charge ISDN users for two subscriber lines.  The FCC feared that revenue losses from subscriber line charges would be passed on to interstate toll rates.  The FCC ruling, however, would result in rate doubling for existing lines.  After public and telephone company outcry, the FCC suspended its ruling subject to the condition that common carrier line rates do not increase.  Now, telephone companies are asking state PUCs for permission to raise rates.  As a result, telephone companies are managing to pound the final nails in ISDN's coffin on their own without the FCC.


      ISDN has the capability to bring together voice, video, and data on a high-speed, two-way network.  A high-speed network capable of bringing together all media can save time and expense for business; create new markets for radio and television; and boost usership on the internet.  The potential for ISDN is vast.  Yet, telephone companies are not managing and marketing it well.  Further, they do not seem to be actively competing with up-and-coming cable modems.  Finally, telephone companies seem determined not to offer ISDN at reasonable rates.  Consequently, ISDN will likely fade into oblivion as a great technology that never was.