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spec: In a small organization like ours where the majority of the staff works within sight of each other , we're used to huddling , talking through an issue , and delegating tasks on the spot . I can do all kinds of concurrent multimedia communications . Unfortunately , the existing mechanisms to support emergency calls that have evolved within the public circuit-switched telephone network ( PSTN ) are not appropriate to handle evolving IP-based voice , text and real-time multimedia communications . However , because the water must be virtually free of suspended particles for this to be effective , it has been proposed primarily as a secondary treatment for ballast water that has already been filtered .