a mine rescue wired-communications device that provides direct two-way communication with loudspeakers between an underground base and a mine rescue squad.
The Sh–1 mine telephone, which is used in the USSR, consists of a base set and two squad sets. The squad sets may be held in the hand or fastened to the work outfit with a spring hook. Semiconductor devices and printed wiring are used in the electrical components of the telephone sets, which are designed to operate with general-purpose cable drums.
The Sh–1 mine telephone is designed for continuous operation at temperatures of 0° to 50°C, at relative humidities of up to 90 percent, and under conditions of exposure to coal dust, foul air, and underground water. The telephone has a communications range of 5 km and operates continuously for 100 hr without replacement of the power source. It is sparkless and, together with its carrying case, weighs 4.8 kg.