This is a rear view of a typical modern computer with onboard video and sound. (onboard means intergraded into the mother board). Some computers may have separate video and sound cards, but the connectors will be the same, just in a different location from what is show above.
This is a close up of the label on the rear panel.
Serial or COM-1 (db9) Used for External Modems and old Mice. Being phased out on newer computers. Replaced by USB.
Parallel (db25) - Used for old printers. Will not be found on newer computers. Replaced by USB.
USB - A universal serial bus (USB) connector is a connector between a computer and a peripheral device such as a printer, monitor, scanner, mouse or keyboard. It is part of the USB interface, which includes types of ports, cables and connectors.
There are several versions of USB connectors, which vary in their DTRs: USB 1.0 with DTR of 1.5 Mbps and 12 Mbps, USB 2.0 with DTR of 480 Mbps, and USB 3.0, or SuperSpeed, with DTR up to 5 Gbps.
USB 2.0 / USB 3.0
Firewire connectors should not be confused with USB connectors, they look almost the same. Fire Wire is used to connect external devices like hard drives. Sometimes Fire Wire is called IEEE1394a or i-link.
Telephone Connector - RJ-12 modular.
Network Connector RJ-45 or Ethernet (8 conductors) -CAUTION - NEVER Plug the Telephone line into the Ethernet port. The Telephone Line Ring Voltage (110V) could blow the Ethernet Card.
Keyboard and Mice Connectors - Old Style 5 Pin DIN Keyboard connector. The 5 pin DIN connectors are rarely used anymore. Most computers use the mini-DIN PS/2 connector, but an increasing number of new systems are dropping PS/2 connectors in favour of USB. Adapters are available to convert 5 pin din to PS/2.
PS2 Keyboard (Purple) and Mouse (Green). NOT interchangeable.
PS2 Adapters for USB Keyboard and USB Mouse.>
USB to PS2 Adapter usually used on laptops for external keyboard and mouse.
Newer Motherboards may have a single PS2 connector with 1/2 purple and 1/2 Green.
Wireless Keyboards and Mice will have a USB transponder which needs to be plugged into one of the USB Ports.
Analogue Video output to monitor. Also called a D-Sub Port
DVI - Digital Monitor Connectors
DVI stands for Digital Video Interface. It was designed to provide an industry standard digital connection between a Personal Computer and a desktop display. Traditional CRT (Cathode Ray Tube) displays use an analogue signal to receive image data from the computers graphics card. For this reason, early graphics cards needed to covert their native digital signal into analogue in order to support CRT monitors.
LCD monitors are digital display devices, but when they were first introduced they needed to be able to accept and adapt this analogue signal to ensure compatibility with the majority of available computers in order for the LCD to accept the computer's analogue output, then the signal had to be reconverted to digital. Since both the computer and the LCD digital monitor accept and transmit digital signals, the process of translating digital to analogue is unnecessary. The DVI digital connection removes this conversion process.
There are two types of DVI connections. DVI-I and DVI-D connectors. DVI-I provides backwards compatibility with analogue displays and supports both digital and analogue connections to the display. The DVI-D supports digital only. A DVI-I cable CANNOT be connected to a DVI-D connector.
Here is a picture of one of the new video cards with VGA and DVI connectors:
HDMI - High Definition Multimedia Interface
HDMI connects both audio and video in a single cable to/from: TV, Blu-Ray Players, HD-DVD Players. Some Computers come with an HDMI connector to provide output to a HD TV or HD Monitor equipped with HDMI input.
SPDIF is a standard for transmitting high-quality digital audio without going through an analogue conversion process. The SPDIF interface can be implemented in two different ways, Coaxial and Optical.
Mini Optical 3.5mm jack
Here is another view of the rear panel of a new ASUS mother board:
SATA and eSATA
SATA is "Serial ATA" or "Serial Advanced Technology Attachment". It is the new interface for connecting Mass Storage Devices and Optical Drives. The SATA connectors are inside your computer and connect the HARD DRIVES and DVD drives to your motherboard. SATA replaces IDE cables and connections.
Newer computers and external hard drives now come with EXTERNAL SATA (eSATA) connections. eSATA is much faster than USB 2.0 and about the same speed as USB 3.0 or Firewire. But speed is not everything.
If you have a choice eSATA it is the better of the three standards. Using USB 2.0, USB 3.0 or Firewire requires first converting the data to a different protocol then back to SATA. The native format for newer hard drives is SATA.
One test conducted that compared the speed difference between USB 3.0 and eSata found that USB 3.0 was about 20% faster at reading a hard drive while eSATA was 20% faster and writing to the hard drive. eSATA has been around awhile and USB 3.0 external hard drives are soon to come.
eSATA ports on the rear of a computer
Laptop Connectors will be almost the same as on a desk top. Below are some pictures of Laptops:
For New Laptops with only one audio jack you need this adapter for Mic and Headset.
Some newer thin laptops may not have sufficient room for all the connectors. In this case you may have to have an adapter cable.
- This page last updated on 5 Aug 2018