Scouters are devices worn by all of Frieza's men to determine the power level of other fighters. This tecnology was given to Frieza by the Saiyans, who stole it from the former inhabitants of their own planet.

Scouters display a person's power level in numbers, but when the Z Fighters aquired one from Radditz, they had to have Bulma get it to display translated numbers first before they could use it. There are other disadvantages to Scouters as well. If there is a power level that is well into the thousands, and the fighter charges up even more and does it quickly, an active Scouter sensing the energy will shatter after a few moments from overload. Also, Frieza had to have a new-model Scouter delivered by the Ginyu Force so he could sense energy levels that were too far away.

It has been said that Scouters could not pick up the energy levels of fighters after the Frieza saga because they got too high. This statement is not interly incorrect, just inaccurate. No one but Frieza's men ever USED Scouters, and once they were all dead nobody had Scouters anymore so they were just never back in the series. Also, although Scouters did have a tendency to shatter with quick power-ups, a new model could have been made to avoid this problem, and also, by turning it off DURING the power-up you could read the power level later.

Scouters also served another purpose: they are communicators. Nappa and Vegeta recived information on Earth from Radditz this way. Also, it can be a clock and a timer. Vegeta gave the humans 3 hours to wait for "Kakarot" to appear and timed it on his Scouter during the Saiyan Saga. They are very versitle pieces of equipment.

Just for a little more info on them, they power levels appear in yellow text with a circle around the person in view or an arrow pointing in their direction if they are out of view. A large "scouter" type mechanism was in Turles's ship, allowing him to see the power level of the entire Earth and see that it was a good place for the Tree of Might. That should cover most of the finer points, but please read on if you wish.

These are 4 different Scouters seen in the series. They come in different colors just to fit the wearer. It's really rediculous, but it reminds me of when they came out with those computers with a color choice. Whoa. (Note that no scouter is yellow because that is the color of the text on them. There was an orange one seen here and there, but it was rare. The darker purple, blue, and green were the most common)

Here's a picture of Nappa and Vegeta facing the sun with gleaming scouters. I just thought I'd show this pic because I happen to like it and it's a good example of them being worn. The glass is in the front over one eye which gives a colored tint to their site, but it's pretty cool. They can also read it without having to look anywhere, just change the focus of their eyes.