Because it locates cellular devices, assigns frequencies, transmits signals to the correct sites, the is probably the most important part of any cellular network.

Mobile switching station

The mobile switching station is the most important part of any cellular network. It is associated with communications functions such as call set-up, release, and routing, locating cellular devices, assigning frequencies and transmitting signals to the correct sites. It also provides useful information such as user registration required to support mobile service subscribers.

imagine a line passing through the center of earth that goes through both the north pole and the south pole. this imaginary line is called an axis. earth spins around its axis, just as a top spins around its spindle. this spinning movement is called earth's rotation. at the same time that the earth spins on its axis, it also orbits, or revolves around the sun. this movement is called revolution.