... scope 1,Working-yard overhaul: Power grid and equipment maintenance, line construction, mining building site, etc.. real-time communication.2, ... one (or more) extension consists of a set, simple operation. In line with the provisions of the Ministry of information industry. 2 ... 700 meters around the host effectively.11. Earphone: ¢ 2.5 connector ear plugs, ear hook headset.12. Extension phone: DC 3 ...