Communication Flashcards
serial data transmission
Method of data transmission
each bit is sent one after another
over a single wire
parallel data transmission
Method of data transmission
Multiple bits (often 8 bits) sent at the same time
over multiple wires
advantages of serial transmission
more accurate/fewer errors over a longer distance
less expensive wiring (single wire)
less chance of data being skewed/out of synchronisation
disadvantages of serial transmission
slower- less data sent at once due to only one wire
advantages of parallel transmission
faster, more data sent at once due to more wires
disadvantages of parallel transmission
less accurate/more errors over a longer distance
more expensive wiring (multiple wires)
more chance of data being skewed/out of synchronisation
serial transmission use
Medium to long distances
Ethernet
Telephone Wire
USB (Universal Serial Bus)
parallel transmission use
Short distances
Fast internal data transfer within a computer system (buses)
IC’s (Integrated Circuits)
Older printers
synchronous transmission
A continuous stream of data
The data is accompanied by timing signals (generated by an internal clock)
The clock ensures the sender and receiver are in step with each other
asynchronous transmission
Data is transmitted in discrete packets (usually 1 byte)
Each packet of data is sent with control bits
The control bits allow the receiver to know when the data starts and ends
The control bits prevent the packets of data getting mixed up
Packets are sent intermittently (they have uneven time intervals between them
duplex data transmission
Direction of data transmission is both ways at the same time (simultaneously)
half-duplex data transmission
Direction of data transmission is both ways but not at the same time (not simultaneously)
simplex data transmission
Direction of data transmission is one way only (unidirectional)
duplex data transmission example
Telephone call
broadband connections video conferencing
half-duplex data transmission example
Walkie Talkie
Intercom
simplex data transmission example
radio/tv broadcast
microphone to computer
computer to speaker
Integrated Circuits
self-contained circuits with many separate components (e.g. transistors, diodes) etched into a tiny silicon chip
Uses parallel transmission for sending data internally in computer systems
Disadvantages of integrated circuits
Less flexible -components cannot be removed or replaced so whole IC must be
Limited power rating
Advantages of integrated circuits
Small size – thousands times smaller than discrete circuits
Small weight due to miniaturised circuit
Low cost due to mass production
Low power consumption because of their smaller size
USB
Universal Serial Bus
Uses asynchronous serial transmission for sending data externally to and from peripherals / between devices
Advantages of USB
Devices plugged into the computer are automatically detected
The connectors can only fit one way- prevents incorrect connections being made
Industry standard-considerable support is available to users
Supported by many operating systems
USB device is plugged into a computer
The computer automatically detects a device (due to a small change in the voltage level)
A known device is automatically recognised, and the appropriate device driver is loaded
If a new device is detected, the computer will look for and install the device driver
If this is not available, the user is prompted to download the device driver
Disadvantages of USB
limited distance
current transmission rate is slower than ethernet
