Data Communication
The Interface in Data Communication
The transmission of a string of bits from one device to another over a transmission line means a high degree of cooperation between both ends.
The receiver must know the speed at which it is receiving the data to sample the line at constant intervals of type in order to determine each of the received bits, it must also know the duration and the separation between the bits, all these characteristics are known as timing.
To transmit through a medium, every device will do so through some interface, this interface also specifies the physical connection. Two techniques are used for transmission:
Line configuration
The two characteristics that distinguish possible data link configurations are the Topology and its operation in Half-Duplex or Full-Duplex.
TOPOLOGY
It refers to the physical arrangement of the stations in the transmission medium. If there are only two stations the link is point by point. If there are more than two stations then it is a topology multipoint. Multipoint links have been used when a computer and a set of terminals were available. They are currently typical of Local Area networks.
Traditional multipoint topologies are only useful when the terminals transmit for a fraction of the time, needing only one I/O port and a single transmission line, thus saving the corresponding outages.
If each terminal had a point-to-point link to its central computer, the central computer must have an I/O port for each connected terminal.
Full Duplex and Half-Duplex
Data exchange over a transmission line can be classified as full-duplex o half duplex. in transmission half duplex each time only one of the two stations on the point-to-point link can transmit. This mode is also called in two alternate senses. alluding to the fact that the two stations can transmit alternately. This type of transmission is used in the interaction between the terminals and the central computer.
In full-duplex transmission the two stations can simultaneously receive and send data, this mode is called "simultaneous two-way" and is used for data exchange between computers.
For digital signaling, where a guided medium is required, full-duplex transmission typically requires two separate paths; while half-duplex transmission needs only one.
When the same frequency is sent or received using wireless transmission, it must operate in half-duplex mode, whereas if a station emits one frequency and receives another, for wireless transmission it must operate in full-duplex mode.