Signal (information theory)

Imagine you wanted to tell your friend something, but you couldn't talk, write or text them. Instead, you decide to use a flashlight to send a message to them. You can turn the flashlight on and off to send a message in a series of flashes, called a signal.

In information theory, a signal is any message or pattern that conveys information. It can be a sound, a light, a vibration or anything else that can be detected by our senses or technology. Think of it like a secret code that is used to pass messages between people without anyone else understanding what they are saying.

The key part of a signal is the information that it carries. For example, if you use your flashlight to send a message to your friend, the information could be what time you want to meet, or where to find the treasure. The information is encoded into the signal using a specific code, such as Morse code, which is a series of dots and dashes that represent different letters.

In information theory, there are different ways to measure how much information is contained in a signal. One way is to look at the number of possible messages that could be encoded using that signal. For example, with Morse code, there are a limited number of combinations of dots and dashes, so the amount of information that can be encoded is limited.

Another important aspect of signals is their reliability. If your flashlight is weak or your friend is too far away, the signal might not be strong enough to convey the information you want to send. In information theory, this is called signal-to-noise ratio, which refers to the amount of unwanted interference or noise in a signal compared to the amount of desired information.

Overall, signals play an important role in communication, technology and many other areas of our lives. Understanding how they work can help us to improve our communication and make better use of technology to share information.