Apresa records telephone calls from the Unify ISDX 3000 using passive recording. During a call, VoIP data is sent to and from the phones. This VoIP data is copied to the call recorder by port mirroring (also known as SPAN). In a Local Area Network, this port mirroring is done by a network switch. The picture below shows internal passive recording. With this setup, Apresa records internal and external calls.