Standard PSTN FXS with RJ-11 400-500Hz Dial-tone and Busy-tone , Disconnect Tone 50V in idle and 75V in ringing and 9-12V in talking DTMF detector in RJ-11 Provide reverse polarity Caller ID (DTMF,after ONE Ring) One Number Unified(Optional) CLIR(Calling Line Identification Restriction) Separate Power On/Off controller LED indicating Hook On/Off,Talking,Signal Intensity,Power On/Off Setable dialing delay time Setable automatic dialing Support to dial all number including of * # DTMF Automaticly dialing (Optional) SPK & MIC volume regulate Provide accumulator charger interface (Optional) Multiparty Calling teleconference (Special Optional) Setable Maxim talking time to warn of exchanger card (Special Optional) 4SIM Rotator Automaticly (Special Optional) IMEI changing (Special Optional) Rasio Bases Changing Automaticly to simulate movement (Special Optional) Simple to install and easy to maintain Steady module & reliable design ensures good performance Strong signals with high gain antenna No noise & Clear voice for wide voltage range & Low power consumption Suitable for all kinds of weather & environment Offer keypad command sets to define functions Product dimension: L455x W280 x H45mm Gift box dimension: L510x W170x H64mm G.W: 4.6kg