An intercom (intercommunication
device) is an electronic communications system intended for limited or
private dialogue, direction, collaboration or announcements. Intercoms
can be portable or mounted permanently in buildings and vehicles.
Intercoms can incorporate connections to
walkie talkies,
telephones,
cell phones and to other intercom systems over phone or data lines
and to electronic or
electro-mechanical devices such as signal lights and door latches.
Permanent intercoms installed in buildings are generally composed of
fixed microphone/speaker units which connect to a central control panel
by wires. A small home intercom might connect a few rooms in a house.
Larger systems might connect all of the rooms in a school or hospital to
a central office. Intercoms in larger buildings often function as
public address systems, capable of broadcasting announcements.
In many schools, tones signaling the change of classes are sounded over
the intercom, taking the place of the electromechanical
bells used in older schools. Additionally many schools now use audio
/ video intercoms to identify visitors trying to gain access to a locked
school building. Many intercom systems can be interfaced with the
building's
access control system.
Traditional intercom systems are composed entirely of
analogue electronics components but many new features and
interfacing options can be accomplished with new intercom systems based
on digital connections. Video signals can be interlaced with the more
familiar audio signals. Digital intercom stations can be connected using
Cat 5 cable and can even use existing computer networks as a means
of interfacing distant parties.
