The ATC (short for Air Traffic Controller) is a very popular and inexpensive belay device. It is light weight, easy to use and allows good control of the rope. Black Diamond also offer a slight variation on the ATC, known as the ATC XP. This offers an increased friction option as well as the standard option available on the regular ATC. In addition there are also a number of other “tube” type belay devices on the market from other manufacturers. These look very similar to the ATC and operate in much the same way.
A Black Diamond ATC.