In UP0e-based user connections the signaling connection (D channel) is separated from the voice connection (B channel) by subdividing the physical medium into time slots and assigning the two connections different time slots. In HFA, the two-wire line is replaced by an IP-based LAN as the physical medium of the digital user connection. The signaling connection between the terminal and HFA (Common) Gateway uses a secure TCP connection and the voice data are transferred via an H.323 connection using the RTP/RTCP protocol. Both connections can now be routed differently in a single LAN. This means it is possible for there to be signaling although the voice connection is temporarily interrupted.

In order to configure an HFA user, primarily it is necessary to determine the following points beforehand: