This is an activity we did in class, learning about the tools for transmitting and receiving. These are notes from the book and my teacher.
Serial Data Transmission: All the data bits travel, in their correct order, one after another along the same connecting link.
- One Bit at a time
E.G.
- USB ( Universal Serial Bus)
- Internet Connections
- Telephone lines
- Travels more distance
Parallel Data Transmission: Each data bit travels along its own connecting path.
- One byte at a time
- Eight bits sent simultaneously
- Can travel faster ( speed)
- Cannot travel far
- Travel distances upto a few metres
E.G.
- Some printer, parallel port
Controlling the flow
---> Signal Directions
Simplex: Data links allow the data to move in only one direction. In a simplex link there is no need for a return data signal.
E.G.
- computer mouse, constant stream of data from mouse to computer, but not from computer back to mouse.
- Computer keyboards ( most)
Half Duplex: Data links allow the data to move in both directions, but not at same time. The receiving device must wait until the sending device has finished before it can reply.
- commonly used
- not fastest
- separate wires for data flow in opposite direction, but receiving device must wait till sender is finished before replying.
E.G.
- normal telephone conversations.
- chatting over the internet ( MSN).
Full Duplex: Data links allow the data to move simultaneously in both directions. Both devices in the link must be able to send and receive at the same time.
- Fastest
- Most efficient way
- Allows both devices to send and receive at the same time.
E.G.
- mobile phone
- computer
- modem
Signal timing
Asynchronous: Communication link has no set times for data to be transmitted or received.
- Every byte sent as separate package of data.
- Single bit also called " start bit ", example, your phone ringing something designed to get the attention of the receiving device
- Last bit also called " stop bit", tells receiving device that transmission of the data byte has been completed. Example, the sound made when other person hangs up the phone.
- Last Bit: Allows device to resume any tasks that were interrupted by arrival of start bit.
E.G.
- Email
-SMS
Synchronous: Communication link use agreed times for data to be transmitted and received.
- Efficient } Faster process
- Faster
- No stop or start bits
- Not as common, because of difficulty of getting two devices ( different) to send data at the exact agreed times, due to fact that these devices are separated by considerable distance.
E.G.
- video conferencing
- telephone calls
Data Speed
Baud: Number of distinct signal events or timing intervals in a second.
Bits per second (bps): Number of bits that are transmitted in a second.
Broadband: Devices that can send and receive more than one signal at a time.
j Bits per second
Broadband Sanea.
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