dual card  terminal GSM/PSTN WTN303-1B  Features:  A,      Use high gain external antenna with high signal sensitivity B,      LCD display, menu operation interface, easy operation C,      Display Caller ID  D,      Barred number setting E,      Auto dial code conversionF,       Support 2 SIM Cards : GSM(A) and GSM (B),Conveniently choose GSM(A),GSM(B) or  PSTN G,      Auto-select Low cost route according setting H,       Five working modes: GSM(A+B),PSTN,PSTN/GSM(A+B),GSM(A),GSM(B)     Technical specifications                            Power supplyAC input voltage           160V~280V ACPower adaptor output        DC7.5V/3.0ABattery                   6V/4AH Lead-Acid batteryoptionalMaximum charging current   600MADC input voltage range       7.5V~10V DCWorking current            1.5A(DC7.5V, Average current, excluding charger current)Application environmentOperating temperature:         0~+45CRelative humidity:            10%~95%Environment noise            ≤60dB(A)Atmospheric pressure         86~106kPa GSM parametersFrequency bands       GSM850/900/1800/1900 MHzFrequency stability        <2.5ppmReceiver sensitivity     < 103dBmTransmit power        <2W(900MHz),  <1W1800MHzSIM card Interface      3VAntenna impedance     50Ω Line interfaceAB line impedance     600ΩAB line loop current    25mAAB line feeding        48V±4V (hang-up status) Package10pcs/CartonInside box          Dimension:32×18.5×5.5(cm) G.W.:  0.7kgExternal carton  Dimension:42×36×32(cm)     G.W. :8.0kg