... professional manufacture in Asia Mining telephone,dust proof telephone KNSP-08L Applications: As Public telephone for indoor or outdoor, Taxi ... Port, Dock, Mines, Generation facilities... A good ideal telephone for use in wet or corrosive atmospheres DTMF(Dual Tone ... 941HzCall transmission index(5KM)SLR<12,RLR<-1,STMR>10, output impedance is 600 Ohm. Mining telephone, dust proof telephone KNSP-08L