Anyone know what a chameleon circuit is? and what it does?

10 points to the best answer.

In Doctor Who, it's the circuit in the Tardis which allows it to change it's appearance in order to blend in to the environment in which it lands.

The chameleon circuit in the Doctor's Tardis is broken, however, and so it is stuck in the shape of an early 1960s London police box.

The chameleon circuit, has however been seen in operation on a number of occasions in the classic series.

In "The Dalek's Master Plan", the first Doctor changes the appearance of the Meddling Monk's Tardis a number of times before making it look like a police box in order to confuse him.

Later, The Master's Tardis was seen in many different guises, and was seen to change it's appearance on landing, on a number of occasions. The Rani's Tardis was also seen to change it's appearance in "The Mark of the Rani"

In the Sixth Doctor story "Attack of the Cybermen", the Doctor actually managed to briefly repair the chameleon circuit of his Tardis. On landing in a junk yard, it changed it's appearance to become a stove, then later it became a rather elaborate looking pipe organ. In other words, it was able to change appearance, but not to blend in very well. So the Doctor finally settled for the old police box shape again.

Are you Robbie Savage?

It enables the outward appearance of a TARDIS to change into something that fits into its surroundings as it materializes. If it fails or stops working, the TARDIS is stuck as the shape into which it last materialized.

Chameleon circuit?????? This is from Doctor Who. It is the circuit which allows the tardis to change its appearance to match it's surroundings. The circuit on the doctors Tardis is broken which is why it is stuck as a 1950's police box.

Oh and it isn't real I am afraid.

A chameleon circuit is a mechanism which is responsible for changing the outside appearance of the TARDIS in order to blend in with the environment. It's a bit like the cloaking technology used by the Klingon's in Star Trek on there war ships like Klingon Birds of Prey and also the Romulan's with there Romulan War Birds.
But the chameleon circuit has been stuck for 44 years or more as a blue police box.

Well, you've had several good answers here - the phrase "chameleon circuit" is from Doctor Who, and is used to explain why a machine capable of travelling through time and space, and which is bigger on the inside than the out, looks like a grotty 1960s police box. It's a form of camouflage device essentially. The Doctor's Tardis has a chameleon circuit that got stuck in 1963 in London, hence the police box. But it's a thing that's been seen in action a few times - as Spacephantom says. The Doctor actually fixed his own chameleon circuit in the Sixth Doctor story "Attack of the Cybermen" - it changed into an organ, and a set of gates. But ultimately it returned to the police box form and has stayed like it ever since.

It's interesting to note that the series first used the idea of the chameleon circuit (if not the name) back in 1963 - three years before Star Trek launched the idea of the cloaking device.