ISDN

ISDN

ISDN is a service that operates at 128 Kbps and is available

from your phone company. Charges for ISDN connections

usually resemble those for analog lines—you pay per call

and/or per minute, usually depending on distance. ISDN

charges also can be flat rate if linked to a local Centrex system.

Technically, ISDN consists of two 64-Kbps channels

that work separately. Load-balancing or “bonding” of the

two channels into a 128-K single channel is possible when

you have compatible hardware on each end of a connection

(for instance, between two of your campuses). What’s more,

as a digital service, ISDN is not subject to the “line noise”

that slows most analog connections, and thus offers actual

throughput much closer to its promised maximum rate.

You can make ISDN connections either with an ISDNready

router or with an ISDN terminal adapter (also

called an ISDN modem) connected to the serial port of your

router. Again, modems are best for single users, because

each device needs its own modem, and only one “conversation”

with the outside world can happen at any one time.

Your ISDN router, modem, or terminal adapter may come

with analog ports, allowing you to connect a regular

telephone, fax, modem, or other analog phone device. For

example, a ISDN router with an analog phone jack would

allow you to make phone calls and send faxes while staying

connected via the other ISDN digital channel.