Serial and Parallel Transmission

Serial Transmission

In, serial transmission, data is transmitted at one bit at a time in a continuous stream along the communications channel. For each direction of data flow, only one wire is used.

This pattern is analogous to the flow of traffic down a one-lane residential street. Most data transmitted over telephone lines uses a serial pattern. Serial Transmission is typically slower than parallel transmission, because data are sent sequentially in a bit-by-bit fashion.

Parallel Transmission

In the case of parallel data transmission, several bits of data are transmitted concurrently through separate communication lines. This resembles the flow of traffic on a multi lane highway. Internal transfer of binary data in a computer uses a parallel mode. If the computer uses a 32-bit internal structure, all the 32 bits of data are transferred simultaneously on 32-lane connections. Parallel data transmission is commonly used for interactitons between computer and is printing unit.

Digital and Analogue Transmission

Data is propagated from one point to another by means of electrical signals, which may be in the digital or analog form. As shown in the figure below,

analog signals are continuous in nature. They have continuous amplitude levels. Since they are continuous, it is very difficult to remove physically any noise and distortion from them, which is added during transmission or otherwise. The telephone lines used for data communication in computer networks are usually meant for carrying analog signals.

A digital signal is a sequence of voltage pulses represented in the binary form. These signals are well-defined with discrete amplitude levels. Computer generated data is digital in form.