1. Match light are multiplexed lines. 800Hz telephone impedance is 800Ω ± 20%. 2 .Through two telephones on the same model, in less than 75db audio noise conditions, the communication distance up to 21 km. 3. In temperature -40 â?? (using cold battery) - +50 â?? 750 ± 30mm Hg pressure and temperature of +40 â??, relative humidity up to 98% of the reliable work environment. 4. All parts are fixed on the rack into one, along with mobile phones are loaded into the enclosure, solid structure to carry and easy to use. 5. Volume : 222*195*107mm3 ã?? 6. Weight : about2.5Kg -