The N-8010RS Substation Interface Unit uses packet audio technology to permit connection of up to 16 RS-1xx series call switches or door stations. Call switches and door stations use the same shielded twisted pair wiring. Each port provides 1W @25v to a door station, or 25V loudspeaker attached to a call switch. Each N-8010RS supports 1 voice link. The N-8000RS requires an IP master station, or connection to a 2-wire or 4-wire Exchange with at least one master station on the exchange.