Transmission modes or data communication modes
The way of data sending from one place to another via communication media is called data communication or data transmission. There are four modes or ways of transmitting data.
A simplex transmission transmits the data in one direction only. This means that you can either send the data or receive the data. For example telegraphs systems, radio broadcasting, television broadcasting. Printer communication is also an example of simplex transmission. The direction may be from the processor to an i/o device, or it may be from a terminal to a processor.
The duplex transmission allows for two-way broadcasting. The duplex mode is further divided into two types:
Half Duplex transmission
In half-duplex transmission we can send or receive the data at a time. For example, a walkie-talkie is a half-duplex device because only one party can talk at a time.
Full Duplex Transmission
In full-duplex transmission data is transmitted from both ends simultaneously means that you can send and receive the data at the same time. For example, a telephone is a full-duplex device because both parties can talk at once. In this transmission, bandwidth is divided in two for each direction of data transmission if the same transmission medium is used for both directions of transmission.
In asynchronous communication, data can be transmitted un continuously rather than in a steady (uniformly) stream. In computer communications between devices for example between the CPU and disk drives and modems and printers are asynchronous. In asynchronous communications, the receiver must be able to distinguish between valid data and noise this is mostly done by sending special bits at the beginning and end of each message. One of the examples is asynchronous communications also include computer-based exchanges of messages or text message on the cell phone for which the participants need not be available or online at the same time but read and also respond when they need.
In the synchronous communication or real-time communication, data is sent in blocks also called packets at the fixed time intervals. An activity that might use a synchronous protocol is the transmission of files from one point to another. As each transmission is received, a response is returned indicating success or the need to resend. For example, can occur only at specific points in the clock cycle. For example, a telephone conversation is synchronous in telephonic conversations each party can talk whenever they want but in the asynchronous communication, each party would be required to wait for a specified interval before speaking.