--------------------------------------------------------------------------------

Modems (MOdulators and DEModulators) take data from the computer and
modulates the data into sounds for transmission over the phone line.  The
modem on the receiving computer demodulates the sounds into data, which is
then send to the connected computer.

The modulation and demodulation process is inefficient.  A better way to
transmit the data is to avoid the mod/demodulation process.  Use digital
lines, and send the data digitally -- essentially, this is the purpose of
ISDN.

ISDN (Integrated Services Digital Network) is an additional *paid* service
from the telephone company.  It is a high bandwidth technology that allows
users to send large amounts of information in short amounts of time.  While
V.34 can send data at 28.8 kbps, ISDN can send data at 128 kpbs.

Basic Rate Service (BRS) ISDN, or 2B+D is composed of two 64 kbit/s digital
channels and one 16 kbit/s control channel.

Some parts © 2009 Advameg, Inc.