The remote control you use to change channels on your TV set works by sending an infra red signal which is picked up by a receiver in the TV and decoded.
On many TV and other remotes the infra red emitter is exposed, it is the small clear globe on the end of the remote. On some units it is hidden behind a dark red window.
Now infra red is a type of electromagnetic radiation like light, but unlike light it is not visible to the human eye. Look at the IR emitter as you press on of the button on the remote control and you will not see anything happen.
So how come I say in the title of this article that you can see the signal your remote sends? Well there is a very simple trick that makes it possible.
Digital cameras can detect infra red, and the processing that takes place in the device means that it shows up on screen as white light.
The easiest way to try this for yourself is with the camera built into a mobile phone, or the webcam built into a laptop computer. Point the remote at the camera, press a key, and see the glow from the IR emitter.
Try it with different remote controls, some produce what looks to the human eye like a constant signal, others pulse.