How Fast Can You Talk?

How Fast Can You Talk?

by Jeff Carrell, E-Mail Liaison

reprinted from Fort Worth Section Signals October 1995

Bell 103 ... modem ... ISDN ... baud ... V.34 ... 9600 ... MNP 4 ... bps ... V.32bis ... BRI ..., you've heard (some of) these terms before, but what do they really mean?

Most of these relate to asynchronous communications, and for this discussion, to/from your computer. However, some of these terms are transmission speeds, some are transmission protocols, and some are just plain new technologies for communications in general.

Although 2400bps modems have been around for a long time (in personal computer life), it didn't start there. The first modems available for PC's were 300 baud (anyone remember?) and even though by today's standards they are slow (like get real, big time slow!), back then I thought that communicating with other computers at 300 baud couldn't get any better. Soon after though, faster speeds became available; after 300 came 2400, then 9600, 14,400 and now the V.34 or 28,800bps modems. One of the biggest problems that arose (and is still experienced today with 28.8Kbps) when these newer modems became available was that the systems you dialed into didn't always support the higher speeds, or they charged more for that privilege (at least some did for awhile).

The term "baud" also became inter-changeable with "bps". But these are not really able to be used that way. Baud rate relates to the number of state changes per second. Initially modems moved one bit of data per state change. But with the coming of compression algorithms being built into the modem hardware, more data can be transmitted per state change and bps is the correct term relating to modem speed.

Now, we also have available (at least its starting to become available) ISDN which is supplied to you by your local telephone company, just like a 'normal' phone line. Within the ISDN construct there are two types: BRI and PRI. BRI normally is (or will be) available for home use and PRI normally is (or will be) available for business use. ISDN will provide transmission speeds starting at 64Kbps all the way through 1.5Mbps. However, the ISDN turn-on charges and monthly phone bill is much more than your standard phone bill you pay today. So even though you want the faster speed, you will pay dearly for it, at least until it is popular enough and readily available in order to drive the prices down.

If you are going to communicate to a BBS, then a modem supporting 9600bps and up will most likely be suitable for your needs. However, if you are going to connect to the 'Net and surf around, then consider 14,400bps or better yet, 28,800bps modems (which would be much better), especially if you plan on doing a lot of surfing and/or file transfers. If you are really hooked on the 'Net, then you may even consider a dial-up ISDN line. If you are doing business on the 'Net, then an ISDN line may be a good, first connection speed. It provides higher connection speeds than typical leased-line circuits (usually a 56Kb) and its monthly bill is cheaper as well.

This chart covers transmission speed standards:

standard speed (bps)

Bell 103 (V.21) 300

Bell 212A (V.22) 1200

V.22bis 2400

V.32 9600

V.32bis 14,400

V.32ter 19,200

V.34 28,800

This chart covers compression and error checking standards:

standard what it does

V.42 provides error correction/control

V.42bis compresses data about 4:1

MNP 4 provides error correction/control

MNP 5 compresses data about 2:1

MNP 7 compresses data about 3:1

Glossary:

'Net acronym for the Internet

bis an extension to the primary standard

bps bits per second

BRI Basic Rate Interface (ISDN.) 2-64Kbps bearer (B) channels (used for digital data) and 1-16Kbps delta channel (used for analog phone)

ISDN Integrated Services Digital Network.

modem modulator/demodulator device allowing computers to communicate over telephone lines

MNP Microcom Networking Protocol

PRI Primary Rate Interface (ISDN). 23-64Kbps bearer (B) channels (used for digital data) and 1-16Kbps delta channel (used for analog phone)

ter an extension to the primary standard

Have a question or want to know more details about e-mail, the Internet or related technologies? Send me a note and I'll cover it in a future article.

If your society would like an Internet presentation, demo, discussion, etc., let me know. I would be happy to give a talk to any interested group (no commercial pitch, just plain 'ole techie talk :-)

Contact me at:

e-mail: j.carrell@ieee.org

snail-mail: Jeff Carrell POB 1593 Hurst TX 76053

phone: 817.595.0343