There are three ways in which electronic communication is classified, one way communication, two way communication or transmission, analog versus digital signals, and base-band or modulated signals. Let’s consider each of these categories in more details.
Basic Types of Electronic Communication:
In simplex communications, the information travels in one direction only. A common example of simplex communications is radio and TV broadcasting. Another example is the information transmitted by the telemetry system of a satellite to earth. The telemetry system transmits information about the physical status of the satellite including its position and temperature.
The bulk of electronic communications, however, is two way . For example, when individuals communicate with one another over the telephone, each can transmit and hear simultaneously. Such two-way communications is referred to as full duplex.
Another form of two-way communications is where only one party transmits at a time. This is known as half duplex. The communication is two-way, but the direction alternates. Examples of half-duplex communication are most radio communication such as those used in the military, fire, police, and other services. Citizens band (CB) and amateur radio are half duplex in operation.
Another way to categorize electronic communications is by the types of intelligence signals transmitted. There are two types of signals; analog and digital. An analog signal is a continuously varying voltage or current. A typical analog signal is a sine wave tone. Voice and video voltage are analog signals.
The other type of transmitted signal falls under the broad general category of digital. The earliest form of both wire and radio communications used a type of on/off digital code. The telegraph used Morse code, whereas radio telegraphy used an international code of dots and dashed. Data used in computers is also digital where binary codes representing numbers, letters, and special symbols are transmitted by wire or radio. The most commonly used digital code in communications is the American Standard Code for information Interchange (ASCII, pronounced “ass key”).
Although digital communication transmission can be made up of signals that originated in digital form, such as telegraphy messages or computer data, analog signals may also be transmitted in digital form. It is very common today to take voice or video analog signals and “digitize” them with an analog-to-digital converter. There are many benefits to transmitting data in digital form.