Basic Signal Theory

In communications technology, signal theory has to do with basic signal processing. What does signals do? Simply put, signals carry information. There are two basic types of signals:

1. Digital signal
2. Analogue signal

Digital signal

Digital signal can be defined as an electrical signal that produces data, stores and processes the data in form of zeroes and ones (0s and 1s). This means that digital signals can only accept discrete values. For example, computers use digital signals.

Analogue signal

Analogue signal generates continuous values, leading to continuous wave pattern. For example, telephone lines use analogue protocols. Other examples of systems that use analogue signals are non-digitized television and radio systems.

The Role of Modems and Protocols in Data transmission

For a computer to transmit data over the telephone line, a special device (the modem) is needed. The modem is a device that enables a computer to transmit data over analogue telephone lines.

Modem is a combination of two words - MOdulator and DEModulator. The modem acts as a modulator when it converts digital signals to analogue signals. When the modem acts as a Demodulator, it converts analogue signals back to digital signals.

Data can be transferred between computers, using what is called protocols. A protocol can be defined as a set of rules that must be obeyed before communication between computers can take place. Specifically, communications protocols are used to transport information from one place to another. It is the set of rules that allows two modems to communicate.

See also Parity Bit and Error checking