The maximum data communication speed the modem can be operated at is defined as K - kilo, bps - bits per second. So 33.6K bps means that the modem can be operated at maximum data communication speed of 33600 bits per second. Most of the newer Electronic exchanges in India support speeds up to 33.6K bps, but actual speeds that a modem can achieve is dependent on the line condition which may vary due to defects in cabling, rusted connections at the junction boxes, improper wiring at your premises, too many instruments connected to the same line etc. So the speed at which the modems can operate may vary widely on lines from the same telecom exchange itself. Under ideal line conditions modem operating at 33.6K bps will take approximately 5 minutes to download a 1 Mb compressed (Zip) file, at 28.8K bps the same file will take about 6 minutes to download and at 14.4K bps it will take about 12 minutes.

Most of the modems now support 14.4K bps fax , defined by ITU V.17 standards, compatible with Group 3 fax machines. Modem fax capability is further defined depending on the fax command set as Class 1 and Class 2. Some modems support only class 1 others support both class 1 and class 2. In Class 1 the fax sending and receiving is controlled by the Fax software, where as in Class 2, the fax operation is controlled by the modem hardware, hence the CPU over head for Class 2 modems are much less. So if you are planning to use the modem for extensive fax operations selecting a modem that supports Class 2 is preferable.

Many modems now has Voice capability, essentially this means that the modem can function as an Answering machine. If you have to go out of office and there is no one to answer the phone you may set the modem, to answer phone call with a pre recorded voice greeting message, and the caller can leave a voice message to you, which will be recorded by the modem, on the hard disk of the computer. Normally the recording of the greeting message and the playback of the voice message is done through the hand set of the telephone connected to the phone jack of the modem. Some modems has Full duplex Speakerphone capability, such modems will have jacks for microphone & speaker, and may be used like a speakerphone for hands free operation, in addition to the answering machine function.

People commonly confuse, the voice capability of modems with the ability to use Voice conferencing software like, Internet phone, Web phone, NetMeeting, CoolTalk etc. Fact is, Voice conferencing over Internet has nothing to do with the voice capability of the modem. Even with voice modem you will need a sound card, normally part of the Multimedia kit, for voice conferencing over Internet. The exception is combo (combination), modems with built-in sound card, these modems usually come as internal modem cards, that are a combination of Sound card + modem, and are more expensive.

Now most of the modems in the market comply with the V.42 & MNP 2-4 hardware based error correction protocols. The data compression is defined by V.42 and MNP 5 or above protocols and is standard in most modems. When buying modems make sure that they support hardware based V.42/MNP Error correction and Data compression.

There is a popular perception, in India, created by some vested interests, that External modems gives better performance than the Internal modems. This is not true, good and bad modems comes in both internal and external variety. Just because the modem is Internal, does not mean it is bad nor that External modems are all good. The fact is many modem vendors make, same model in both external and internal versions, and both versions give the same performance.

Buying modem

Using modem