This equipment ought to be operated by well-qualified workers who are familiar with the safety rules and know how to make use of the machines properly to avoid dangerous. (drilling underground)Underground, in the coalmine, there are some machines which help miners to output the coal. They are: longwall shearer, boom-type roadheader and coal crusher. The 1st device is called longwall shearer. It is a mining machine, which works underground, in the so-called mining wall, or in the place where the coal is directly output. It moves using the special conveyor (called scrapers); it does not make use of caterpillars (such as boom-type roadheader). The CM user works such a device by the remote control. (see roof bolter)The 2nd equipment applied underground is called boom-type roadheader. It moves making use of caterpillars and works below ground where drills roadways in the mine. Its front side with the tool drills the stone and move ahead. The obtained coal is transferred at the bottom of the boom-type roadheader.The last device, which will be provided in this article, is known as coal crusher. It is an instrument used for crushing coals into smaller parts. Here are machines for crushing mineral coal and brown coal, too.