... impedance: 75Ω,Audio Compression G.726, G711, ADPCMAudio Input1 channel, RCA port, liner input, Impedance:1KOhmsAudio Output1channel,RCA port ... , linear outputAudio talk-back input1 channel ,MIC portOverlaid CaptionChannel Name, Date, Bit rate, position ... or NC (normally close) sense.Alarm Output 4 channel on/off output,120VAC 1A/24VDC 1AAlarm MessageSending alarm ...