¶ … Communications
Synchronous data communication between sender and receiver occurs at regular or predetermined intervals, the timing of which is usually governed by a microprocessor clock. Asynchronous communication occurs intermittently at irregular intervals rather than in a steady stream. In the absence of clocking, a start and stop bit may be employed at the beginning and end of each piece of data (Webopedia, 2011).
Analog describes a device or system that represents changing values as continuously variable physical quantities. When used to describe data storage and transmission, analog format allows information to be transmitted by modulating a continuous transmission signal, such as amplifying a signal's strength or varying its frequency to add or take away data. In general, humans experience the world analogically. Digital describes any system based on discontinuous data or events. Computers are digital machines because at their most basic level, they can distinguish between just two values, 0 and 1, off or on. All data that a computer processes must be encoded digitally (Webopedia, 2011).
XON and XOFF are flow control codes representing data transmission on and off states. XOFF is used by a receiving device to let the transmitting device know to stop transmitting. When the device is ready to recommence, the XON character is sent. This flow control mechanism is used extensively by low-speed devices such as older printers and dumb terminals, to indicate that they are temporarily unable to accept more data. Typically this restriction is due to a combination of limited output rate and buffers being full. With most environments, XOFF is achieved...
An example of this type of service is transmission of burglar alarm messages. Duplex transmission allows data transfer in two directions. Most duplex links are classified as either half duplex, which transmits in either direction, but not simultaneously, or full duplex, which allows both the local and remote node to transmit simultaneously. A telephone line is capable of full duplex transmission, but most human users adopt a half duplex procedure to alternate between speaking and listening (Fairhurst, 2001).
Serial vs. parallel transmission: Serial communication is the process of sending data sequentially, one bit at a time, over a communication channel or computer bus. Parallel communication allows several bits to be sent as a whole. The communications links across which computers or parts of computers talk to one another may be either serial or parallel. A serial link transmits a single stream of data, while a parallel link transmits several streams of data simultaneously along multiple channels (Jeff, 2008).
Baseband and broadband transmission are ways of allocating the capacity of transmission media. Baseband devotes the entire capacity of the medium to one communication channel, and is the most common mode of operation. Baseband signaling can be used with both analog and digital signals. Broadband enables two or more communication channels to share the bandwidth of the communications medium. Cable TV is an example of a broadband medium.…
