USB
USB is the most common data interface used at this time. USB supports a very wide range of devices including external storage devices, webcams, input devices like keyboards and mice, and much more. There are many different common connections used for USB devices, but other than being physically shaped different they all provide the same function.
USB (Universal Serial Bus) is a very common data port that is used for a very wide range of peripherals. Some of the supported devices include external storage devices,
webcams, printers, scanners input devices like keyboards and mice, and much more. There are many different common connections used for USB devices, but other than being physically shaped different they all generally provide the same function. USB is much faster than previous, commonly used data ports. Another benefit of USB is that it is able to supply power at 5V DC and 500mA. This allows the USB port to power low-power devices so that you don't have to plug the device into any other power source.
Detailed Specifications:
There are different revisions of the USB spec. The different versions primarily change the supported speeds of the data connection. Here are the different speeds:
Low Speed (USB 1.0) - 1.5Mbit/s
Full Speed (USB 1.1) - 12Mbit/s
High Speed (USB 2.0) - 480Mbit/s
Super Speed (USB 3.0) - 5000Mbit/s
USB supports a maximum standard cable length of 16 feet. Using passive USB cables longer than this can result in improper function of the USB device. You can get around this problem by using active USB extension cables. These cables have repeaters in them that allow the signal to be repeated to longer distances.
Each USB port can only physically connect to one device. The design of the system, however, allows you to use a USB hub to split that one USB port into several, allowing you to connect many USB devices to a single port. This creates the ability to easily expand the number of USB devices can be connected to a single computer.
Various connectors:
There are several different USB connector types. USB A is the connection found on computers. USB B and mini-B are the most common connectors found on USB devices. Below are the 4 most common connector types, but many more exist as some companies design their own versions for their products.
 USB A |
 USB B |
 USB Mini-A |
 USB Mini-B |
Serial
Serial is an older data interface that is being phased out, but is still commonly used due to how popular it once was. Serial is not nearly as fast as USB or other current data interfaces. Serial is most commonly used with a DE-9 (commonly, but incorrectly called DB-9) connector. It can also be found with a DB-25, 8-pin mini-din, and some other less common connectors.
The Serial Port is a data communication port that has been widely replaced by USB at this point. Serial is still used in legacy applications, mostly with industrial equipment. Serial communication means that it sends one bit at a time. Many popular data connections use the serial communication method. The term Serial Port, however, most commonly refers to a port that communicates using the RS-232 standard.
Some of the most common uses for the serial port have been to connect external data/fax modems, old mice, label printers, PDAs, and various manufacturing and testing equipment. Lots of A/V equipment including audio receivers, cable boxes, DVRs, TVs, etc, include an RS-232 serial port on them which can be used to update or reconfigure the equipment if needed.
There are a few different standards that are commonly used with a serial port.
- RS-232 - The most common serial communication standard for Serial Ports
- RS-422 - A high-speed system similar to RS-232 but with differential signaling
- RS-423 - A high-speed system similar to RS-422 but with unbalanced signaling
Running serial a long distance can cause problems with degradation in the signal quality. To resolve this issue you can use serial extenders which will run the signal over CAT5 cable and allow you to make much longer runs.
Another common issue people run into is the fact that newer computers do not generally have serial ports on them. If your computer does not have serial, but you need to communicate with a serial device you can use a USB to Serial adapter to add a serial port to that computer. This will allow you to communicate with serial equipment as if you had a true serial port on the computer.
There are several physical ports that have been used for serial communication. Here are a few of the most common:
- DB-25 - The original port used for the RS-232 Serial Port
- DE-9 - This port is commonly mislabeled as a DB-9 port and is the most commonly used port
- Mini Din-8 - This port was used primarily by the companies Apple and SGI as a serial port on their systems
Parallel
Parallel is a data type that uses several different connectors. Parallel is faster than serial due to it's ability to send multiple bits at a time, but is older and not as fast as USB. Parallel is being phased out and most devices are switching to the USB interface. Parallel was most commonly found being used with printers, but was also used with many other types of devices. On the computer side of the interface parallel uses a DB-25 connection. For the device side there are several common connectors such as: DB-25, Centronics, Mini-Centronics.
The Parallel port is another data interface that was very popular on computers, but is widely being replaced by USB. Parallel ports are often referred to as printer ports or centronics ports. Over the years there have been many different standards and revisions of the parallel type port. The standard that is most common at this point is the IEEE-1284 standard.
The IEEE-1284 standard was released in 1994 and since then has been the primarily used standard for parallel ports on personal computers. IEEE-1284 superseded the various previous standards that were in use at the time. The standard specifies a maximum throughput of 4Mbps (2Mbps is typical actual throughput).
After this standard was released many devices besides printers began to be adapted to function on parallel ports. Scanners, tape drives, modems, and hardware locks for expensive software packages all became very common.
With parallel ports being replaced by the much faster USB port most computers do not come with parallel ports installed. There are several options available for connecting older parallel equipment to these computers.
If you need to connect a standard printer to the computer you can use a USB to parallel printer adapter. If your printer has built in copy or scan functions, or if you're trying to connect something different all together, you'll need to connect it to a real parallel port.
For desktop computers you would want to use a PCI Parallel Card. That card would get installed in the desktop computer and will add a true parallel port to the computer to run your parallel device.
If you need to connect a parallel device to a printer it can usually be done through either a PCMCIA card or an ExpressCard. These cards do provide true LPT ports that will work with most equipment. Some legacy equipment may not work properly through these adapters due to limitations of the technology. For a laptop that has a PCMCIA slot you would use the Quatech Parallel PCMCIA Card. For a laptop with an ExpressCard you would use the Quatech Parallel ExpressCard.
The standard connector for a parallel port on the computer side is the DB-25 Female type port. Various parallel devices will often use the DB-25 port on them. Printers often use the Centronics 36 type connector while some will use the Type C, MDR36 (Mini-Centronics) type.
FireWire
FireWire is a fast data connection that is used for a wide range of devices. While it is a fairly common connection it is not as common as USB. One of FireWire's main uses is with digital video cameras, but is also used with external storage and other devices. FireWire commonly comes in both 400Mbps and 800Mbps versions. The 400Mbps version uses both a 6-pin and a 4-pin type connector. The connector for the 800Mbps version is a 9-pin connector.
FireWire
Developed by Apple in the 80’s, FireWire—originally called IEEE 1394—is a means of high speed communication and data transfer between computers. FireWire is often used with external hard drives and video cameras for the fastest transfer speeds. They are connected to the computer through a FireWire card and FireWire cable. FireWire cards are a standard on both desktop computers and laptops and are found as either 4-circuit connectors or 6-circuit connectors. These connectors can be distinguished by their respective size, with the 4-circuit being smaller.
FireWire cards come in several interface formats in order to accommodate different types of computers and motherboards. Users can identify which interface format to purchase by understanding the different types and what type of computer technology they have.
Desktop Computers
Desktop computers are equipped with a motherboard that allows for expansion and upgrade by inserting different peripheral cards. The most common are PCI and PCI Express cards. PCI cards can be identified by the longer surface area that plugs into the motherboard slot. There are usually several PCI slots on the average motherboard and the user simply needs to slide the PCI FireWire card into a corresponding spot in order for the card to function.
PCI express cards are characterized by the smaller connection point that slides into the PCI Express slot on a motherboard. The connection point is typically at the end of the card and measures only about an inch long. There are typically less PCI Express slots on a motherboard than PCI and therefore users should make sure they have an empty PCI Express slot available before purchasing a PCI Express FireWire card.
Laptop Computers
Laptop computers will often have a FireWire connection point built directly into the computer. This connection is built into the motherboard and can be found by locating either the 4-circuit or 6-circuit connector. Most laptops will have the smaller—4-circuit—connector to save space on the computer.
For laptop computers that do not have a built in FireWire connection, users have the option of installing either a FireWire PCMCIA card or a FireWire ExpressCard. These cards can be installed through a card slot most often located on the side of the laptop.
PCMCIA cards, or PC Cards, are an older technology that is the width and length of a credit card. Users with a FireWire pcmcia card simply need to slide the card into the corresponding slot in order for the card to function.
The other laptop connection card format is the ExpressCard. They are a newer technology and have become the standard on laptop computers. They come in two sizes, 33mm and 54mm wide and slide into the corresponding laptop slot. It is important to note that the PCMCIA card and the larger ExpressCard are both the same width. Therefore it can be difficult to determine which card is compatible with a user’s individual laptop.
For each of the interface formats discussed it is important for the user to first determine which connection their computer has. This information can be found through the computer manual, the computer website, or by viewing the connection and determining the size of the card needed.
Ethernet
Ethernet is used to connect your computer to other computers and the internet. Ethernet is a fast connection designed for this purpose alone. Ethernet uses an 8P8C (RJ45) connector. Ethernet speeds commonly range from 10Mbps to 1000Mbps. It most commonly runs on cat5 cable, but can also be used on cat6 and other types of cable.
GPIB
GPIB is a name for the IEEE-488 interface. IEEE-488 has been around for a very long time and is most commonly found on measurement and test equipment. IEEE-488 is a parallel type data bus. It supports up to 15 devices with a max Bandwidth of 1Mbps (up to 8Mpbs on updated equipment). IEEE-488.2 defined the commands to control equipment so that it could be standardized between different equipment manufacturers.
SCSI
SCSI is an older data interface that was used for both internal and external equipment. There is a large number of different SCSI interfaces and speeds. SCSI has always been a fast interface in comparison to other available interfaces, but has also generally been more expensive because of this. SCSI has a lot of benefits to it including the ability to hook up to 16 devices on a single bus, high speeds, error checking. The benefits from SCSI make them more commonly used in high end machines like servers where the performance is worth the extra cost.