UI 770 Interface Box 1,5 V C-Battery (IEC LR 14 C) Phone connecting cable: 4/4 modular plug (RJ9) Technical Data Frequency response: Speaker signal output to phone: 100Hz. to 7kHz Microphone signal output to phone: 100Hz to 7kHz Microphone signal output to phone: 0mV to 300mV adjustable Audio output level: Speaker signal output to phone: Limited to 400mV.
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