Intercom

Digital intercom stations can be connected using Cat 5 cable and can even use existing computer networks as a means of interfacing distant parties.Performing arts venues such as theaters and concert halls often have a combination of permanently mounted and portable intercom elements.Multiple channels of simultaneous conversations can be carried over additional conductors within a cable or by frequency- or time-division multiplexing in the analogue domain.Portable intercoms are connected primarily using common shielded, twisted pair microphone cabling terminated with 3-pin XLR connectors.Digital intercoms use Category 5 cable and relay information back and forth in data packets using the Internet protocol suite.This type of format allowed the two channels to operate in standard microphone cable, a feature highly desired by the broadcasters.This reconfiguration was usually handled at a central location, but because voltage is used on the circuit to power the external user stations as well as communicate, there would usually be a pop when the channels were switched.So while one could change the system on-the-fly, it was usually not desirable to do so in the middle of a production, as the popping noise would distract the rest of the television crew.There may be concerns about privacy since conversations may be picked up on a scanner, baby monitor, cordless phone, or a similar device on the same frequency.A single device can add intercom functionality to multiple standard telephones on a common phone line, even of different makes and models.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 used CDMA (Code Division Multiple Access) technology.
1980s MirTone intercom system
An intercom control desk
Intercom used for team and driver communication in Formula One
Intercom system in the Pittock Mansion
A butler uses an intercom on behalf of a lady
Sub-station by Bolinder's Teleradio (1950s)
A modern four-wire intercom system capable of 272 sources and destinations manufactured by Telex Communications Inc.
Loudaphone brand intercom station aboard RMS Queen Mary . The Loudaphone was specified for noisy environments such as aboard trains and trams and within a ship's engine room.
Intercom (company)Nurse call buttonpublic telephone networkpublic address loudspeaker systemswalkie talkiestelephoneselectric strikeTCP/IPanalogue electronicsCat 5 cableaccess controltrainswatercraftaircraftarmoured fighting vehiclesFormula Onespecial event production crewsprofessional sportsPerforming arts venuestheatersconcert hallsrace tracksemergency medical techniciansmotorcycle helmetscitizens band radioPMR446Bluetoothmesh basedPittock Mansionparty-linepush to talkinterruptible feedbackearpieceheadphonesdirect currentfrequency-time-division multiplexinganalogue domainpacket-switchedtwisted pairXLR connectorsCategory 5 cableInternet protocol suiteoutside broadcasttelevision crewFour-wire circuittelevision studiotelevision stationstelevision networkswireless intercomPower line communicationRMS Queen Marykey telephone systemsWestern ElectricCourtesy telephoneDoor phoneVideo door-phonePublic address systemSpeaking tubeTank phoneVoice chat in online gaming