Draytek NT22P

4-Port ISDN TE/S0 Module f/ Vigor 3510 This module provides two switchable TE/S0 ports and two fixed S0 ports. The S0 ports (sometimes called NT ports) )are for connection to an existing ISDN PBX trunk port (input). This is useful where you do not wish to replace your existing ISDN PBX yet but want to have the benefits of VoIP. You can also connect ISDN phones to the S0 ports. The two switchable TE/S0 ports can be set to be either S0 or TE mode so the module can provide either 2 S0 +2TE ports, or four S0 ports. When the two switchable S0/TE& ports are set to TE mode, they are for connection to ISDN2e lines (as per fixed TE module above).