intercom

An intercom, also called an intercommunication device, intercommunicator, or interphone, is a stand-alone voice communications system for use within a building, small collection of buildings or portably within a small coverage area, which functions independently of the public telephone network. Intercoms are generally mounted permanently in buildings and vehicles, but can also be detachable and portable. Intercoms can incorporate connections to public address loudspeaker systems, walkie-talkies, telephones, and other intercom systems. Some intercom systems incorporate control of devices such as signal lights and door latches. Intercoms are used on a wide variety of properties, from houses that only require one connection between a resident and the property's entrance to multi-unit apartments that require intercom hardware to be installed in every individual apartment. Some are equipped with video and its wiring (electrical installation) can be connected to the outside with a few pairs (4-6 pairs) while controlling an electric strike. The latest generations are even compatible with computers and some models include TCP/IP compatibility.

An intercom, also called an intercommunication device, intercommunicator, or interphone, is a stand-alone voice communications system for use within a building, small collection of buildings or portably within a small coverage area, which functions independently of the public telephone network. Intercoms are generally mounted permanently in buildings and vehicles, but can also be detachable and portable. Intercoms can incorporate connections to public address loudspeaker systems, walkie-talkies, telephones, and other intercom systems. Some intercom systems incorporate control of devices such as signal lights and door latches. Intercoms are used on a wide variety of properties, from houses that only require one connection between a resident and the property's entrance to multi-unit apartments that require intercom hardware to be installed in every individual apartment. Some are equipped with video and its wiring (electrical installation) can be connected to the outside with a few pairs (4-6 pairs) while controlling an electric strike. The latest generations are even compatible with computers and some models include TCP/IP compatibility. ==Permanent systems== Traditional intercoms and public address 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 carried as well as voice. Digital intercom stations can be connected using Cat 5 cable and can even use existing computer networks as a means of interfacing distant parties. Intercom cameras can be used in modern offices and hotels. Many schools and office buildings now use audio/video systems to identify visitors trying to gain access to a locked building and can be interfaced with the building's access control system. Besides fixed locations, intercom systems are used on many types of vehicles, including trains, watercraft, aircraft and armoured fighting vehicles. ==Portable systems== Portable intercoms are commonly used by special event production crews and professional sports teams. Performing arts venues such as theaters and concert halls often have a combination of permanently mounted and portable intercom elements. Motorsports race tracks often have both portable and permanent intercom stations mounted at critical points around the racecourse for use by race officials and emergency medical technicians. Portable intercoms are also used for motorcycle communication, for example, between motorcyclist and passenger, bike-to-bike communication or communication within a pack of riders. Intercom mounting systems can be attached to most motorcycle helmets. Several different types of technologies can be used, including various types of citizens band radio like for example PMR446, Bluetooth, or dynamic mesh communication (DMC) which is a mesh based intercom system developed for motorcycle communication. ==Telephone intercoms== Some telephones include intercom functions that enable paging and conversation between instruments of similar make and model. Examples include Panasonic model KX-TS3282W(/B), AT&T models 945 and 974, and TMC model ET4300. A single device can add intercom functionality to multiple standard telephones on a common phone line, even of different makes and models. Installation effort is minimal, and is not vulnerable to the radio interference and security issues of wireless systems. The Add-A-Com Whole House Intercom for Standard Telephone Systems is such a device. Intercom paging is accomplished by sounding a distinctive ring from all telephones after any phone is taken briefly off hook. After paging, any number of phones may converse. The device temporarily disconnects the external phone line during intercom use, and reconnects when all phones are again on hook. During intercom use, an external call’s ringing signal can be heard in the earpiece. Many key telephone systems for office use provide access to multiple outside lines plus an intercom, where the latter appeared as if it were one of the individually selectable lines. The Western Electric Model 207 and Model 6A intercoms were designed for integration into such key system multiline installations, providing one or two simultaneous intercom calls, respectively. ==Cell phone intercoms== A cell phone network intercom is an outdoor device that communicates wirelessly over the cell phone network with any landline or mobile phone worldwide. Often called GSM intercoms, they initially used the Global System for Mobile Communications standard, and the intercoms were first released in European countries. This standard is now used globally, though in the United States, primarily AT&T, T-Mobile, and a few other providers use GSM, while Sprint and Verizon use CDMA (Code Division Multiple Access) technology. Modern cell phone intercoms support all carriers and the latest technologies. Commonly installed at gates or doors, they are popular because they eliminate the need for wiring, except for power. ==See also== Courtesy telephone, a telephone for relaying messages to a specific person after being notified via a public address system, or for customers to seek information Door phone, electronic device for communication with someone outside a building Video door-phone, audiovisual communication device enabling visual identification of a visitor Public address system, a system for distributing the voice of an announcer over a large area Speaking tube, an air pipe through which speech can be transmitted over an extended distance Tank phone, similar device used in Tanks and Armoured vehicles Voice chat in online gaming ==References==

Text derived from https://en.wikipedia.org/w/index.php?oldid=1367036834 under CC BY-SA 4.0; modifications have been made.