Check the listing for details. Viking electronics FXI-1A Fxo, Fxs Paging Adapter. Condition: New. Listed at 145.82 USD. Viking universal paging interface Select: FXO (loop start), FXS (ring trip) or paging port (VOX relay) interface mode No power supply required in FXS interface mode Up to 6 units can be powered from one adapter in the FXO or VOX mode 30V DC talk battery for interfacing with FXO or unused phone system line input/trunk port Floating 600 ohm paging output with volume control Normally open or closed relay for external paging amp activation or interfacing the paging amp with an external background music source 800 Hz pre-announce page tone (on/off) Compatible with 24 to 48 volt FXS operation Calling party control (CPC) detection for immediate disconnect Busy signal detect disconnect 2.5 to 5 second VOX silence disconnect timer Programmable VOX trigger sensitivity 16 or 36 second default disconnect timer Screw terminal block connections Wall mount housing: (2) #6x3/4 panhead screws included Power: 12-24V DC @ 100mA, 120V AC/12V DC @ 500mA, UL listed adapter included (not required in FXS mode) Dimensions: 111mm x 76mm x 36mm (4.38” x 2.97” x 1.38”) Shipping Weight: .48 kg (1.06 lbs) Environmental: 0°C to 32°C (32°F to 90°F) with 5% to 95% non-condensing humidity Relay Contacts: 30V DC@1A, 110V DC@0.3A, 125V AC@0.5A VOX Minimum Audio Signal to Activate Relay: -30dbm minimum / -26dbm minimum @ 1KHz with VOX sensitivity switch at normal / lower positions VOX Time Out Disconnect: 2.5 or 5 second Default Time Out Disconnect: 16 or 36 seconds Talk Battery: 30V DCVKFXI1