How to get the max speed from your modem:

Now there is a different speed which is separate from the above modem to modem speed, and that is the modem to computer speed (DTE speed). When you are using a modem it is usually connected to your computer and you have some type of communication program you are using which talks to the modem. This program tells the modem to dial a number, and it then allows you to do your business via telephone. The speeds which the modem can speak to your computer must be one of:115.2Kbps, 57.6Kbps, 38.4Kbps, 19.2Kbps, 14.4Kbps, 9.6Kbps, 4.8Kbps, 2.4Kpbs, 1.2Kbps and 300bps. Some of these speeds are the same as the DCE speeds above and some are not. The modem which you are calling is also connected to a computer. The DTE speed of the computer you are calling cannot be determined by you on your end. You have no control over it. What you do have control of is the DTE speed to which your computer is hooked to your modem, and this speed is critical to efficient and fast communication.

Generally, you should tell your communication program to use the fastest possible DTE speed when speaking to your modem. Most modems can speak at 57.6Kbps, some can speak at 115.2Kbps, others, older types, must speak slower. You must examine the user manual which came with your modem to determine the maximum allowable DTE speed, and set your communication program accordingly.

The next thing which is extremely important is to tell your communication program to use 'hardware handshaking'. Every modem requires being told to use 'hardware handshaking' and most communication programs know what command to send to the modem to accomplish this. If your communication program doesn't ask what brand of modem you are using or doesn't have your particular modem in its list, then it is up to you to find the proper command in your modem manual and enter it in the appropriate place in your communication program. Basically 'hardware handshaking' means that your modem and your computer agree on when to start and stop communicating using one of the wires in the cable you have them connected with. When your DTE speed is very high (like 57.6 or 115.2) there are times when your computer - regardless of how fast the processor is inside it, just can't keep up with all the information your modem is sending it. The computer needs a way to tell the modem "hey, stop for a moment while I catch up". The computer send a signal on the wire (wire is hardware) and the modem sees this signal and pauses. If it needs to, it tells the modem which it is speaking to to pause also, and that modem might tell the computer it is speaking to to pause also. Perhaps it is called 'handshaking' because all the equipment in the line, computer to modem, modem to modem and modem to computer need to cooperate with each other.

A logical question you might have is, if the modem to modem speed (DCE) is only 28.8, why would you need to have your computer speaking to your modem (DTE) at 115.2? The answer is in those funny little modem descriptions such as "V.34", "V.FC", "V.32bis" and others. These are protocols (or standards) in which the modems compress the data which is being fed it by the computer to allow it to get out over the telephone lines at (for instance) 28.8. Modems of the V.34 protocol can compress what is being fed it by 4 to 1. This means if your computer is sending data extremely fast to the modem (as in 115.2) the modem has the ability to compress that by 4 to 1 (115.2 / 4 = 28.8) and send it out over it's 28.8 DCE speed. The receiving modem takes that 28.8 DCE data, expands it back to it's original form (which in this example was 115.2) and sends it off to its computer. This is why the highest possible DTE speed is necessary for efficient use of a modem.