Serial and Parallel Direct Cable Connections are considered to be a bit "old fashioned" these days. USB Direct Cable Connection (DCC), on the other hand, belongs in the "new fashioned" category. USB DCC is a few years old, but because most people would use their network card to transfer data, the DCC hasn't been very well known for the USB port, but does exist.... and the catch is that you can't make it, but you must buy it ! But don't be tempted to leave the page just as yet there is a lot of information on USB which is always good to know. Keep reading -- we'll take a closer look and see what it's all about!
USB stands for Universal Serial Bus. Most peripherals for computers these days come in a USB version. The USB port was designed to be very flexible and for this reason you are able to connect printers, external hard drives, CDROMS, joysticks, scanners, digital cameras, modems, hubs and a lot of other cool stuff to it.
The Universal Serial Bus gives you a single, standardized, easy-to-use way to connect up to 127 devices to a computer. The 127 number is a theoretical number :) In practice it's a lot less! The devices you connect can even power through the USB port of your computer if they draw less than 500mA, which is half an Ampere (I). A good example is my little Canon scanner, it only has one cable which is used to power the scanner up and to transfer the data to the computer!
Currently there are two versions of the USB port, the initial version which is USB v1.1 and the newer version...
The table below compares the two USB ports so you can see the speed difference:
Keep in mind that when you're using a USB DCC cable, you won't get such great speeds, but somewhere around the 500 Kbps. This also depends on the type of CPU, O/S, the quality of the cable and electronic components and protocols running on your system. Another thing which you should keep in mind is the Windows Operating System that supports the USB port:
The USB cable
The USB standard uses A and B connectors to avoid confusion. "A" connectors head "upstream" toward the computer, while "B" connectors head "downstream" and connect to individual devices. This might seem confusing to some, but it was designed to avoid confusion between consumers because it would be more complicated for most people to try and figure out which end goes where.
This is what the USB cable and connectors actually look like:
As mentioned earlier, the USB port can power certain devices and also transfer data at the same time. For this to happen, the USB port must have at least four cables of which two are for the power, and two for the data.
The diagram is to help you understand what the cable contains:
The USB DCC (finally)
As I mentioned in the introduction of this page, the USB DCC cable cannot be made, because it requires special electronic circuits built around the cable. Parallel Technologies manufacture USB DCC cables and they call it the "NET-LinQ":
The USB DCC cable can also be used to connect a computer to your network. The way it works is pretty simple. Assuming you have Computers A, B, C and D. Computer A, B and C are connected via an Ethernet LAN and Computer D hasn't got a network card to connect to the network. Using the NET-LinQ or other similar cables you can connect Computer D with any of the other 3 computers as long as they have a USB port, then by configuring the network protocols on Computer D, it will be able to see and connect to the rest of the network!
This completes the discussion about USB direct cable connection.
Cabling tips for network professionals series
Lesson 1: Network history and fundamentals
Lesson 2: Straight-through UTP cables
Lesson 3: CAT5 UTP crossover cable
Lesson 4: 10Base-T/2/5/F/35 - Ethernet
Lesson 5: 100Base-(T) TX/T4/FX - Ethernet
Lesson 6: Fiber cable
Lesson 7: Direct cable connection
Lesson 8: Serial direct cable connection
Lesson 9: Parallel direct cable connection
Lesson 10: USB direct cable connection
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This was first published in September 2007