Electronic Media - Published 10/07/96



Talking on the Phone: A modem Guide 



By - Joe Fedele





Have you ever overhears a couple of computer jockeys brag about the speed of their modems 

and wish someone would translate?



I'm here to help.



First off, here is some basic info to get you started.



The introduction of e-mail and the Internet have made modems a 

vital part of our computer world.  



Modems "modulate" and "demodulate" (hence the word: mo-dem) information such as digital 

signals from a computer so they may be transmitted over an analog network. 



For most of us this analog network is a standard dial-up telephone line, now referred to by many 

as Plain Old Telephone Service or POTS, by many.  



The speed a modem runs at is generally referred to as the Baud Rate.  Computers operate in a 

world of digital "on" and "off" pulses called "Bits".  A set of bits, usually 8 per set, is called a 

"Byte".  



Modems are often differentiated by their highest baud rate. A modem capable of operating as 

high as 14,400 bits per second is generally referred to as a 14.4K modem.  But a 14.4K modem 

can also operate at 9.6K or less if it is forced to adjust is speed to a lower baud rate.  Modems 

will automatically adjust their speed for a number of reasons.



Some businesses' phone systems restrict the bandwidth of their line.  



This translates into slower speed handling capabilities for 

modems.  If you just bought a top of the line 33.6K modem and 

can't figure out why your connections never gets past say 28.8K, 

you might find the telephone system itself is the bottleneck.



The quality of your connection to systems on the outside world 

can also effect the speed of your modem.  Newer modems have the 

ability to sense deteriorating and improving conditions on a 

POTS connection and will automatically adjust baud rates down or 

up accordingly.



Like many computer users, my investment into the new 

technologies seems to be a never ending quest for a faster, 

easier, and more powerful way to work, play and communicate.  



I'll not soon forget the day I purchased my first 300 baud modem - a several hundred dollar, 

add-on investment to my new "high tech" Atari 800 computer, which by the way, was 

"loaded" with a dazzling 48K of memory, gave me access to other places, people and computer 

systems around the world.



Both computers and modems have come a long way since then. 



So much for the days when 2400 baud modems cost over $300 and were considered to have 

crested the limits of POTS line speed handling capabilities.  Today you can pickup a 14.4K 

modem for less than $40 and 28.8K modems have just dropped below the $100 mark.



Next month I'll take a look at  how ISDN lines and modems have surpassed POTS to 

revolutionize Internet access.