Microsoft Office Tutorials and References
In Depth Information
Data Communications
Figure 24
Computer expansion ports
power plug socket
mouse port
keyboard port
USB ports
serial port
parallel port (printer)
speaker and
microphone jacks
monitor port
modem port
network port
A parallel port transmits data eight bits at a time. Parallel transmissions are relatively
fast, but increase the risk for interference, so they are typically used to connect a printer
that is near the computer. A serial port transmits data one bit at a time. Typically, a
mouse, keyboard, and modem are connected with serial interfaces.
SCSI (pronounced “scuzzy”) stands for small computer system interface . One SCSI
port provides an interface for one or more peripheral devices. The first is connected
directly to the computer through the port, and the second device is plugged into a similar
port on the first device. SCSI connections can allow many devices to use the same port.
They are particularly popular on Macintosh computers and notebook computers.
Figure 24 shows some other ports for telephone cables to connect a modem, a video
port to connect a monitor, and a network port. The interface to a sound card usually
includes jacks for speakers and a microphone, which are designed to work with a MIDI
(musical instrument digital interface) card , which is pronounced “middy.” MIDI cards are
used to record and play back musical data.
Notebook computers may also include a Personal Computer Memory Card International
Association (PCMCIA) device . PCMCIA devices are credit-card-sized cards that plug directly
into the PCMCIA slot and can contain additional memory, a modem, or a hard disk drive.
Another type of port found in computers is a USB (Universal Serial Bus) port . USB is a
high-speed technology that facilitates the connection of external devices, such as joy-
sticks, scanners, keyboards, video conferencing cameras, speakers, modems, and printers,
to a computer. The device you install must have a USB connector , a small rectangular
plug. You simply plug the USB connector into the USB port, and the computer recognizes
the device and allows you to use it immediately. USB-compatible computers work more
like stereo systems, in that you don’t have to completely disassemble the unit to add a
component. Any USB device can use any USB port, interchangeably and in any order. You
can “daisy chain” up to 127 devices, plugging one device into another, or you can con-
nect multiple devices to a single inexpensive hub. Data is transferred through a USB port
10 times faster than through a serial port, for example. For many USB devices, power is
supplied via the port, so there is no need for extra power cables. Older computers can
have numerous connectors—a keyboard connector, a mouse port, a parallel port, a joy-
stick port, two audio ports, and two serial ports. USB computers replace this proliferation
of ports with one standardized plug and port combination.
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