Wireless intercoms are wired differently from each another. From the analogue intercoms to portable intercoms and also to digital intercoms, conversations are sent and received in a way unlike from others. However with these wireless intercoms, communication is still done in a convenient way.
Most of the analogue intercoms carry voice signals with 1 or 2 volts through conductors atop power rails with direct current of 12, 30 or 48 volts. The signal lights are through extra conductors or through tone frequencies of the main voice that are sent either on top or below the audio frequency band. For multiple conversations over many channels, the signal are carried through added conductors or though frequency/time-division multiplexing in analogue field. Also, multiple channels are transmitted over signals of packet-switched digital intercoms.
As for the portable intercoms, connections utilize shielded, twisted pair of microphone cables and terminated through 3-pin XLR connectors. Similar connections are employed by vehicle and building intercoms although shielded cabling consist many twisted pair instead of just one. And in digital intercoms, Category 5 cable is used and delivers and receives conversations in Internet-protocol-architecture data packets.
Just like the popular wireless intercoms of today, there are two intercom systems that are popularly utilized by TV stations and broadcast vehicles like those used to cover sporting events and such in previous years. These two intercoms are the two-wire party line and four-wire matrix systems. During the early years, TV stations use old phones for communication system but this was improved to the off-the-shelf systems of today’s intercoms.
The system of two-wire line party was common during late 1970s to mid 1990s which use a 32 Volts of impedance generating power supply transmitted to outside drive stations or even belt packs. This two channel type has made operation of two channels using the standard microphone cable possible. Usually comes with a limited flexibility and capacity of being hardwired but are easily maintained and operated with a durable design. However, the user would converse with one person or group and cannot communicate with others until the system was reconfigured otherwise.
Reconfiguration was then done with two-wire routers or with source-assigned panels at the central location of the system. But since the circuit use voltage for communication and external station power there are pops occurring as the channels switched. Although this changing of system is not recommended while a production is in operation for the popping sound would likely sidetrack the other production crew.
The four-wire intercoms have become more widely known during the mid 90s as the technology designed smaller and sold at a cheaper price. This four-wire technology may be present for some time but since implementation needed a lot of money, it was not very popular. These intercoms were only utilized by large stations and TV networks for it needs large physical footprint within the television studio. However compared to wireless intercoms, the wireless systems have gained more distinction.