... including FXO, FXS, 4-wire E&M, 2-wire E&M, V.24, etc. All plug-in replaceable cards could be inserted ... flexible.Features1. Dual power supply is available.2. All plug-in cards are replaceable. Users can replace the faulty cards ... 31Signalingchannel associated signalingFXO/FXS interface Physical connector RJ45Frequency range300Hz~3400HzImpedance 200Ω+560Ω//0.1μFComplianceITU G.711 A-LawLoop current ...