Intercom is mainly applied in the public security, civil aviation, transportation, water conservancy, railways, manufacturing, construction, service, etc, used for group among the members of the contact and command scheduling, in order to improve the communication efficiency and improve the emergency ability of fast reaction. Along with the intercom into civil market, people go out tourism, shopping is also becoming increasingly use intercom. In addition, a few specific situations intercom, such as explosion intercom, waterproof walkie talkie, police intercom, etc. The table may also include the use of radio category.