PA over IP refers to PA paging and intercom systems that use an Ethernet or GSM-R network instead of a centralized amplifier to distribute the audio signal to all paging locations in a building or campus. Network-attached amplifiers and intercom units are used to provide the communication function. At the transmission end, a computer application transmits a digital audio stream via the local area network, using audio from the computer's sound card inputs or from stored audio recordings. At the receiving end, specialized intercom modules (sometimes known as IP speakers) receive these network transmissions and reproduce the analog audio signal. These are small specialized network appliances addressable by an IP address just like any other computer on the network.
Such systems are inter-connected by the networking infrastructure and thus allow loss less transmission to remote locations across the Internet or a local area or campus network. It is also possible to provide for multiple or relocatable transmission control stations on such a network.
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