From Salt Air
By David Terry


What is v.32? What's the difference between it and v.42?

The v.32 standard is a "modulation" standard. I like to compare it to the AM
and FM standards used in radio broadcasting. Not only are they at different
frequencies but they use different modulation techniques. There are different
modulation standards for 300, 1200 and 2400 baud. The v.32 standard is a full
duplex (data going both ways simultaneously at the rated speed) standard for
4800 and 9600 bps connections.

The v.42 standard is an error correction standard. It is a method by which
data is packetized and sent between modems to ensure that the data that arrives
at the receiving end is the same as what was transmitted. It also includes the
ability to compress data on the fly to enable higher throughput without
requiring a different modem modulation scheme.

MNP is another error correction standard. In fact, the v.42 standard includes
MNP as an "alternate" method in case a modem is not v.42 compliant .. in other
words v.42 modems can connect with MNP modems and achieve a "reliable"
connection.

A commonly asked question is if v.32 modems will work with v.42 -- and the
answer is yes and no. If you asked the question "can I transmit ENGLISH over
an FM RADIO FREQUENCY and have the listeners understand" the answer would be
the same and for virtually the same reasons (comparing the v.42 method of
packetizing data to English and the v.32 method of modulation to FM).

The v.42 and v.32 standards are for two completely different (but
complimentary) areas of communication. In fact, you'll most likely discover
that every v.32 modem you find has v.42, MNP or some other kind of error
correction control built into it.

So... a v.32 modem can talk to a v.42 modem -- if the modem on the other end is
a v.32 modem and if it can understand the v.42 method of packetizing data (or
the MNP method since MNP is included in the v.42 standard).