AX-4S Features | Specifications | Packing 4 Basic Rate Interface ports (I.421) for TE and NT mode Hardware DTMF detection Conference bridge PCM bus connectors daisy chaining of max. 4 cards 4 dual-color LEDs (layer 1 state indicators) Active channel switching (across multiple cards over the external PCM bus) TRB3/TRB3-A1 certified Point-to-Point (TE/NT) and Point-to-Multipoint (TE/NT) EuroISDN protocol stack Suitable for 3.3 volts and 5.0 volts 32 bit PCI 2.2 slots Application: ISDN BRI PBX ISDN least cost router Voice over IP BRI gateways VoIP integration of ISDN equipment PBX to PBX trunking IVR AX-4S PCI card x 1