OfficeIntercom Communication Software 

OfficeIntercom lets you use your computer to speak to others over the internet or your local office computer network. It works like a virtual intercom.
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BellCommander 

BellCommander is a powerful network intercom system which plays audio to PC speakers, PA systems, and client PCs. BellCommander is a great low cost replacement for school bells, intercom systems, store audio solutions, and multi-room audio systems.
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ESDi 

Talk to one or more people at the same time via your PC using this intercom application. Designed for your local area network. Talk directly to a particular person or talk to a group.
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