Signals tell machines what to do — Engineering, 4–6
A button, light or sound can carry a simple message that makes a machine start, stop or change.
Messages for machines
A machine cannot guess what we want. A signal gives it a small message, such as start, stop or go this way. Pressing a button, covering a light sensor or hearing a beep can all be ways of sending that message.
Why use signals?
People needed a way to control machines without pushing every moving part by hand. A signal lets a person give a clear instruction from a little distance, or lets a machine notice something has changed. The problem is turning an action or event into a message.
A button controls a fan
First, the fan is off. Next, press the button once: the button sends a start signal, and the fan turns on. Press it again: it sends a stop signal, and the fan turns off. One small action has changed what the machine does.
The machine did not understand
It is easy to think that a button always tells a machine exactly what we mean. That feels natural because people understand gestures and tone, but a machine follows only the signals it was designed to recognise. A wrong button, missing signal or broken wire can cause a different result.
Signals all around us
A lift button calls a lift, a traffic light tells drivers when to stop, and a doorbell tells someone that a visitor is waiting. Washing machines use buttons and lights too. In each case, a small signal helps people and machines coordinate an action.
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