communication Flashcards
name four different types of data transmission
simplex, duplex, half duplex, full duplex
what is the definition of simplex data transmission
data is transmitted one way only
what is the definition of duplex data transmission
two or more connected devices that can communicate with one another in both directions
what is the definition of half duplex data transmission
data is transmitted both ways but not at the same time
what is the definition of full duplex data transmission
data is transmitted both ways at the same time
state the two differences between serial and parallel data transmission
serial transmission - one bit is sent at a time over a single wire
sends data externally between devices
parallel transmission - multiple bits are sent at the same time using multiple wires
sends data internally
give an example of serial transmission
computer to printer
give an example of parallel transmission
computer to modern
give an advantage of serial transmission
reliable over long distances
less errors since it only uses one wire
give an advantage of parallel transmission
- faster than serial transmission
- more reliable over short distances
what are the reasons for using serial transmission to connect devices to a PC
- single wire means less chance of errors
- a single wire is cheaper
- reliable over long distances
what does USB stand for
universal serial bus
what is USB
it is used as a data transmission method
what kind of transmission do USB use
asynchronous serial transmission
what are the advantages of USB
the devices are automatically detected
they only fit one way so they cannot be connected incorrectly
backward compatible
supports different transmission speeds
what are the three factors that need to be considered when transmitting data?
- direction of data transmission
- method of data transmission
- method of synchronisation between two devices
give an example of half-duplex transmission
a phone conversation between two people but only one person is speaking at a time
when is parallel transmission usually use in the internal electronics of a computer system?
pathways between the CPU and the memory use it
integrated circuits, buses use this form of transmission
what is asynchronous data transmission?
when data is sent in an agreed bit pattern
data bits (1 and 0) are sent together with control bits
having control bits mean that the receiver knows when the data starts and when it ends
this prevents the data being mixed up
what is synchronous data transmission?
when the data is sent in a continuous stream (without being grouped)
data is sent with timing signals generated by an internal clock
this makes sure that the sender and the reciever are synchronised with eachother
how does synchronous data transmission work?
the receiver counts how many bits (1 and 0) were sent
this is reassembled into bytes of data
what is a disadvantage of synchronous data transmission?
the timing must be accurate since it doesn’t have any control bits
what is an advantage of synchronous data transmission?
it is faster than asynchronous which is why its used for important issues (eg network communication)
what does a USB cable consist of?
- four wired shielded cable
- two of the wires are used for power and earth
- two of the wires are used for data transmission
state the disadvantages of USB
maximum cable length is 5 metres
older USB standard may not be compatible in the future
