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Narrator: When you're trying to detect a wavelength of light that our eyes can't see, like infrared

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light, you need to use a detector that can tell you that it's there. The simple

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circuit we're building here can receive a signal in infrared light and convert into sound.

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You'll need a photocell or solarcell with two wire leads,

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and audio cable with a headphone jack on one end and

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wire leads on the other, two test leads with jumper clips at each end,

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and an amplifier/speaker.

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We'll star with the photocell. Gently attach one of the jumper

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clips onto each of the wires coming from the photocell.

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Now do the same with the wires on the audio cable,

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clipping the other ends of the leads onto each one. It doesn't

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matter which wire you clip each one onto as long as you've made a complete circle.

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Now plug the other end of the audio cable into the jack marked

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input on the amplifier/speaker. That's it, you've built a circuit that

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receives the infrared signal from a source--such as a remote control--and sends

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that signal to the amplifier/speaker which turns it into sound.

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