Data communication is the transmission of digital messages to external devices. If you look around your house, you will see many examples of data communication at work. Your cable system, your home phone and even your computer all work based on varying types of data transfer. The process of transmitting a message occurs millions of time a day without any of us being aware of it. Today's recent data transfer methods include many complex concepts, but we can still break down the process to a few basic types.
Simplex
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A simplex communication system sends a message in only one direction. The message source works as the transmitter. It sends the message over the data channel to the receiver. The receiver is the destination of the message. Examples of simplex data communication include radio stations and TV broadcasts. With the simplex channel, there is no ability by the receiver to respond to the message. For example, a radio station plays a song on your car radio. The data transferred is the song. You do not have the opportunity to send a message back via your car radio to the station.
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Half Duplex
A half-duplex data communication system provides messages in both directions but only allows transfer in one direction at a time. Once a party begins sending a transmission, the receiver must wait until the signal stops before responding. If the two data transfers attempt to send at the same time, they both fail. For instance, if you talk on a CB radio, you press a button and speak. If the receiver attempts to press the button and speak at the same time, neither one of you hear either message. The system is not capable of sending both ways simultaneously.
Full Duplex
A full duplex is a communication that works both ways at the same time. Essentially, full duplex data communication is a set of two simplex channels, one works as a forward channel and the other as a reserve channel. The two channels link together at some point. An example of a full duplex communication system is a landline telephone. When talking on a telephone, both parties have the ability to speak at the same time. The data, carried both ways through the telephone line, runs simultaneously.
Serial
Serial communication takes a data communication, breaks it up into small pieces, and sends the message one bit at a time through a channel. The receiver collects the small bits and reassembles them to compose the original message. Serial communication is the most common type of communication between electronic devices. One example of serial communication in action is the data sent from a modem to the service provider.