Null modem, also called crossover, is a term associated with serial (RS-232) cables. A standard serial cable, also called an AT cable, has the wires inside the cable running straight through. Take a DB9 cable as an example. Pin 1 on one end of the cable would be connected to Pin 1 on the other end. Then Pin 2 to 2, 3 to 3, and so on. Null modem cables are serial cables that use an alternative pinout for different functionality.
“Pinout” is a term describing how an electrical cable is wired. Some cables do not have pinouts because they only contain a single internal wire, like coax cables. But if a cable has multiple pins on the end of the cable, it will have a pinout.
Each type of multi-pin cable has a standard pinout or two, but these layouts are not set in stone. Some machines will require non-standard pinouts; this will require users to use a custom cable.
Pinouts also come into play when using a cable with two different ends. For example, going from DB9 (9 pins) to DB25 (25 pins) will mean the DB25 side has 16 unused, “dead” pins.
If you need to know what pinout a cable needs, ideally there will be a spec sheet h
Every type of cable has a maximum distance. These distance limits can vary greatly from one type of cable to the next. Along with determining whether a cable will work, distance limits will also determine how well a cable works. Knowing the fundamentals behind cable distance limits is the first step in selecting the best cable for your needs.
Cables will always have some sort of “maximum signal” rating, depending on the type of the cable. For ethernet cables, it will be the maximum upload/download speed. For HDMI, it will be the maximum resolution of the video. And so on and so forth for other cables. Any type of “maximum” rating should be taken with a grain of salt.
Those ratings are the best possible rating the cable is capable of under t
Computer cables (data cables) are somewhat similar to audio and video cables. Instead of transmitting sound or images, they send data for your computer to use. This can be anything from sending over a Word document to streaming movies and TV shows. Technically ethernet cables fall under this category, but ethernet is such a broad topic it needed its own independent article. Common types of data cables include:
USB is the most common type of data cable today, being found on computers, printers, hard drives, cell phones, and more. Along with transmitting data, USB is commonly used to recharge batteries on cell phones and other devices like video game controllers.