How to Choose the Right Serial File Transfer Cable

A serial file transfer cable can be used to transmit data between two computers via their serial ports. It is also known as a "null modem" cable. These cables are available in several different varieties; buying the right type for your computer is important.

First, look at the back of both computers which you plan to connect the cable to. The serial port has nine pins (DB9) and is normally a "male" port. A few computers have it on the front panel, but this is rare. If both computers have a male serial port, the right type of serial file transfer cable is a "female-to-female" or "F-F" cord. Be sure not to purchase a "male-to-female" serial cable to use for this purpose; these are extension cords for serial mice and old CGA monitors. However, a viable alternative for file transfer is to use a regular serial cable along with a "null modem adapter".

If one computer lacks a serial port but does have a 25-pin parallel (a.k.a. "printer") port, buying a serial to parallel null modem cable (DB9 to DB25) is appropriate. This may also be the best option if one computer's serial port is occupied with a modem or mouse, but it has a free parallel port. Almost all computers have a "female" parallel port, so the parallel (DB25) end of the cable should be "male". Parallel to parallel file transfer cables are also available, and perform the same function as a serial file transfer cord.

Most such cables are six or ten feet long, although some shorter and longer cords can also be found. It usually costs no more than a $2-3 dollars to purchase a cord that is a few feet longer, so it's worth paying if you might need the extra length at some time. File transfer cables are available in colors to match almost any computer system, including gray, beige, and black. They typically have two screws on either side of each end, for (optionally) attaching the cable more securely to computers. Remember not to connect or disconnect the cable when the computer is powered on.

Not many stores offer file transfer cables, but a number of web sites sell them inexpensively. Depending upon the length and port types, buying a cable of this type will usually cost about five to fifteen dollars; I recently bought a new ten-foot file transfer cable from an eBay Stores seller for $4.70, including the shipping cost.