Thanks to Mr. Leong for pointing me regarding the usage of handphone in Clean room. Clean room is the hard disk production room. I will post some of the pictures of clean room. Handphones are not allowded in clean room because the electromagnetic wave will affect the quality of the hard disk produced. Furthermore, electromagnetic signal is used to write/read on the media/disk. So imagine the havoc that a person can cause by bringing handphone inside the clean room.