PORTS, CABLES AND CONNECTORS USED WITH COMPUTERS PART 1

 PORTS USED WITH COMPUTERS

A port is a term in computer hardware, which denotes an interface on a computer to which you can connect a device. Personal computers, servers, smart phones etc…, have various types of ports. A port is a generic name for any connector on a computer or peripheral into which a cable can be plugged, and generally refers to the female part of a connection.

When referring to a physical device, a port (hardware or peripheral), is a hole or connection found on the front or back of a computer. Ports basically allow computers to access external devices such as printers, external storage, scanner, monitor etc….

Common Computer Ports

For a computer to be useful and have as much functionality as possible there must be a way to transmit the data into and out of it. There are different ports available for connecting devices to our computer to enable these functionalities, and before connecting any devices, we should look for types of ports that can be found on our computers.

In brief, these are eight most common types of ports you will see on a computer:  Universal Serial Bus (USB), FireWire (IEEE 1394), eSATA, Video port (VGA, DVI and HDIM), Ethernet, Audio Port (Digital/Analog Sound In/Out), and PS/2 (for keyboard and mouse). 

Serial and Parallel Ports

Two of the most common ports on the back of your computer are the serial ports and the parallel ports. Most computers have one parallel port and two serial ports. They are used to connect different types of devices to your computer.

Parallel ports send data over multiple wires simultaneously, while serial ports only send data over one wire at a time. Since parallel communication allows for multiple streams of data, it provides higher data transfer rates than serial communication. . A parallel port is a type of interface found on computers (personal and otherwise) for connecting peripherals. It is a parallel communication physical interface, also known as a printer port.

 

Parallel ports were implemented on the personal computer when it was introduced by IBM in 1981. They used nine wires in cable to connect two devices together. This enabled them, at any given time, to deliver eight bits of data. However, because there was no way to accurately control the flow of the signal down each of the wires in the cable, it was recommended that the length of the cable be less than six feet.

The standard for bi-directional communication was delivered in the IEEE-1284 specification, which allowed for high-speed communication over the parallel port. This also opened two new specifications for the port: the Enhanced Parallel Port (EPP) and the Extended Capabilities Port (ECP). The EPP-type parallel port was used primarily for non-printer peripherals, while the ECP-type parallel port was designed to accommodate new high-speed printers and scanners. In order to better handle high-speed data communication, the ECP-type parallel port

Serial ports, on the other hand, deliver data sequentially down a single wire. Eight bits of digital data are converted into analog data using a system called baud. Baud rate refers to the number of state changes (tones) that are made on the wire in any given second. This is very different from bits per second (bps), which measures the amount of data that is transferred.

Depending on the baud rate used to transfer data, the length of the cable can range up to 5,000 feet. For data transfer rates at 9,600 baud, the maximum cabling length is 250 feet. The RS-232C standard, which is used as a basis of serial communication, recommends a maximum cable length of 50 feet.

Low-cost processors now allow higher-speed, but more complex, serial communication standards such as USB and FireWire to replace RS-232. These make it possible to connect devices that would not have operated feasibly over slower serial connections, such as mass storage, sound, and video devices.

Serial ports are generally built into the mother board, which is why the connectors behind the casing and connected to the mother board by a wire cable can be used to connect an exterior element. Serial connectors generally have 9 or 25 pins and take the following form (DB9 and DB25 connectors respectively). Many personal computer motherboards still have at least one serial port, even if accessible only through a pin header.

Universal Serial Bus (USB) Port

USB was created in the middle of 90’s as a new release of the serial standard, to standardize communications between computers and peripheral devices. The goal of USB was to revolutionize the way serial communication was conducted. In an effort to fulfill this goal, USB uses a new cabling system that allows up to 127 devices to be connected together.  

There are four different types of USB computer ports: USB 1.0 and 1.1 released between 1996 and 1998 with a speed range starting from 1.5 Mb/sec up to 12 Mb/sec. Then USB 2.0 was released in 2000 with a maximum speed of 480 Mb/sec, USB 3(3.0 released November 2008 and 3.1 released January 2013) was released in 2008 with a maximum speed of 5 Gb/sec. Finally, USB Type-C that was developed at roughly the same time as the USB 3.1 but of different specification.

FireWire (IEEE 1394)

One of the goals of the IEEE-1394 standard (high Performance Serial Bus, is an electronics standard for connecting devices to your personal computer) was to replace SCSI.  While not as prevalent as USB ports, FireWire port has crept into the mainstream and is included as a standard attachment in small numbers, often only one, on motherboards and laptops.

FireWire is an Apple trademark for the IEEE-1394 standard. The 1394 standard implements a version of serial communication across a wiring network that is similar to USB. IEEE-1394 enables the connection of 64 devices and popular due to its ease of use, isochronous (synchronized clock) mode, and very high (400Mbps to 3.2Gbps and higher) transmission rates.  

FireWire (also known as i.LINK in Sony’s parlance) uses a very special type of six-wire cable for FireWire 400. Only four wires are used when power is not supplied by the interface. These interfaces are collectively known as alpha connectors.

eSATA

Short for External Serial Advanced Technology Attachment eSATA is a SATA (SATA is a computer bus interface for connecting host bus adapters to mass storage devices such as hard disk drives and optical drives) connector accessible from outside the computer, to provide a signal (but not power) connection for external storage devices. Prior to eSATA, external hard drives were connected via USB 2.0 or FireWire. While eSATA can provide faster transfer rates than USB or FireWire, it requires its own power connector. 

On a desktop computer the port is simply a connector, usually mounted on a bracket at the back accessible from outside the machine, connected to motherboard sources of SATA, USB, and power at 5 V and 12 V. eSATAp combines the functionality of an eSATA and a USB port, and a source of power in a single connector. eSATAp can also supply power at 5 V and 12 V.

Video Port

A video port (alternatively referred to as a graphics port), can be used for connecting a computer monitor to the computer, or it can be used for connecting a television to the computer. Desktop computers typically position the video port on the back, while laptop computers can position the video port on the back or side.

While the video port analog VGA-spawned standards might keep the computing industry satisfied for years to come yet, the sector in the market driving development of non-VGA specifications has become increasingly more prevalent. These high-resolution, high-performance junkies approach video from the broadcast angle. They are interested in the increased quality of digital transmission. For them, the industry responded with technologies like DVI and HDMI. Let us discuss the functionalities of these video port standards one by one.

*VGA: In its simplest sense, a VGA (Video Graphics Array) port is a 15-pin, D-subminiature style port usually located on the back or side of a laptop computer or the back of a desktop system. Users employ VGA ports to transfer analog video signals from one machine to another using VGA cables. The arrangement of the 15 pins on the VGA port is in three groups of five pins, lined up horizontally.

The port is the "female" version of the pair, meaning it appears as a series of holes, while the cable is the "male" version with the appropriate pins. VGA ports first appeared in 1987 and are analog components capable of carrying red, green, blue, horizontal sync, and vertical sync (RGBHV) video signals.

As the oldest and most widely used type of modern video connector, the VGA port and cable provide a basic video feed. Its counterparts, the DVI cable and HDMI cable, offer digital video and the transmission of larger uncompressed data sets. In the case of VGA ports, the quality, age, condition, and even brand of a VGA cable directly impact the viewing experience in ways that do not affect viewing with the other types of video cables.

*DVI: DVI Digital Visual/Video Interface is a technology developed in an effort to leave analog VGA standards and return to digital video that can basically transmitted farther and at higher data quality than analog, The interface do transmit uncompressed digital video and can be configured to support multiple modes such as DVI-D (digital only), DVI-A (analog only), or DVI-I (digital and analog).   

DVI-D cables (True Digital Video) are used for direct digital connections between source video (namely, video cards) and LCD monitors. DVI-A (High-Resolution Analog) are used to carry a DVI signal to an analog display, such as a CRT monitor or budget LCD. The most common use of DVI-A is connecting to a VGA device, since DVI-A and VGA carry the same signal. DVI-I cables are integrated cables which are capable of transmitting either a digital-to-digital signal or an analog-to-analog signal. This makes it a more versatile cable, being usable in either digital or analog situations.

DVI is a popular form of video interface technology made to maximize the quality of flat panel LCD monitors and modern video graphics cards. It was a replacement for the short-lived Plug and Display standard. DVI cables are very popular with video card manufacturers, and most cards nowadays include one or two DVI output ports.

DVI standard was, for a short while, the digital transfer method of choice for HDTVs and other high end video displays for TV, movies, and DVDs. Likewise, even a few top-end DVD players have featured DVI outputs in addition to the high-quality analog Component Video. The digital market has now settled on the HDMI interface for high-definition media delivery, with DVI being more exclusive to the computer market. 

*HDMI :High-Definition Multimedia Interface (HDMI) is an all-digital technology that advances the work of DVI to include the same dual-link resolutions using a standard HDMI cable but with higher motion-picture frame rates and digital audio right on the same connector.  The HDMI connector is not the same as the one used for DVI. Nevertheless, the two technologies are electrically compatible.

It is known for transferring uncompressed video data and compressed or uncompressed digital audio data from an HDMI-compliant source device, such as a display controller, to a compatible computer monitor, video projector, digital television, or digital audio device.

HDMI cables should meet the signal requirements of the latest specification. As a result, and as with DVI, the maximum cable length is somewhat variable. For HDMI, cable length depends heavily on the materials used to construct the cable. Passive cables tend to extend no farther than 15 meters, while adding electronics within the cable to create an active version results in lengths as long as 30 meters. Twisted-pair and fiber cabling options can extend cabling to 50 meters and 100 meters, respectively. HDMI cabling also supports an optional Consumer Electronics Control (CEC) feature that allows transmission of signals from a remote control unit to control multiple devices without separate cabling to carry infrared signals.

HDMI technology is the de-facto standard for connecting HD equipment. Virtually every TV, AV receiver, DVR, Blu-ray Disc player, and set-top box sold today comes standard with at least one HDMI connection. You’ll also find HDMI connectors on a growing list of other products including gaming consoles, camcorders, digital still cameras, and mobile devices, giving you even more options on how you connect to the expanding universe of HD entertainment.

Ethernet Port

An Ethernet port is an opening on computer network equipment that Ethernet cables plug into. These ports are alternatively called jacks or sockets. Ethernet ports accept cables with RJ-45 connectors.  An Ethernet port allows the creation of networks using wired connections. This socket, which looks much like a large phone jack, allows the insertion of an Ethernet cable. Ports and cables are typically used only to connect devices at a close range, such as in the same building, due the impracticality of laying miles of cabling across town, or hundreds or thousands of miles of cabling across continents.

Most computers include one built-in Ethernet port for connecting the device to a wired network. All popular broadband routers feature Ethernet ports. An uplink port (also called WAN port) is a special Ethernet jack on routers used specifically for connecting to a broadband modem. Wireless routers include a WAN port and typically four additional Ethernet ports for wired connections. Many other types of consumer gadgets now also include Ethernet ports for home networking.  Examples include game consoles, digital video recorders and even some newer televisions.

Many newer computers have a built-in Ethernet card, which allows the creation of wireless Ethernet networks that do not require cabling, substituting wireless technology. For devices without an Ethernet card or dedicated port, a port may sometimes be created by attaching an Ethernet adapter, or “dongle,” to a USB port.

One disadvantage to a physical Ethernet port is its susceptibility to damage and difficulty of repair. It is important to be very careful when inserting or removing a cable from the port, as physical elements of the port can be damaged.

Audio Port (Digital/Analog Sound In/Out)

An audio port on a computer is any receptacle or jack to which an audio device such as speakers, headphones or a microphone can be connected. All laptops and some desktops have built-in speakers, but for better sound or privacy, you will need to connect external audio through one of the ports.

An audio port is attached to a sound card which is an internal computer component that processes audio files in order to provide high-quality playback through computer speakers. It plays voice as well as music files and can handle various audio file formats, including .wav, .mp3 and .cda to name but a few. The quality of the sound card and speakers both affect the overall sound quality of the computer system. The typical card has an interface available at the back of the computer with various input and output audio ports, including the speaker plug.

Most cards also have a line-in port for listening to or recording from an external device such as a digital audio player. If the source device does not have a line-out port to connect to the sound card, a stereo cable can be run from the headphone jack on the source device to the line-in port on the card. Software configurations may be required to hear the device playing.

PS/2 Ports (for keyboard and mouse)

The PS/2 connector is a smaller 6-pin mini-DIN connector used for connecting some keyboards and mice to a PC compatible computer system and is usually referred to as the mouse port or keyboard port. This mouse interface originally appeared in IBM's "Personal System/2" computers in the late 80's and it remains a widely-supported interface. 

The PS/2 designs on keyboard and mouse interfaces are electrically similar and employ the same communication protocol. However, a given system's keyboard and mouse port may not be interchangeable since the two devices use a different set of commands. Though, manufacturers sometimes opt for a single PS/2 connector with half purple and half green color codes, indicating either device can be attached to the same interface, but in these situations, only one of the two types of device can be connected at a time.

Many new PCs you can purchase today contain a PS/2 keyboard connector as well as a PS/2 mouse connector right above it on the motherboard. But today, the PS/2-style connector remains somewhat popular, but it is quickly being replaced by USB-attached keyboards or mouse. Compare your PC’s keyboard connector with the connectors in the diagram above.