The telephone is compatible with most of analogue or digit telephone distance control exchanger. IP and VOIP version optional. Mainly used as handset free sound telecommunication in hazardous work environment, and can realize one-to-one (single key) or one-to-more(more than two keys)as emergency telecommunication, through public communication web and personal web. 1. Main body with whole aluminum alloy with stainless steel front plate, 2 .Handset free, double loudspeaker, with indicator display while speaking. 3. Lightening protection to ITU-T recommendation K.21 4. The keypad can be chosen from 1 to 18 or more. Illuminated buttons optional 5. Adjustable 7 minute timeout optional 6. Waterproof grade is IP65 7. Support hotline call, can realize ring off automatically by the receiver 8. The design is super thin and smart. Embed style and hanging style can be chosen. 9. Every call is limited(set by five minutes),auto ring off if time exceeded. 10.With armored cable to telephone system. 11.The telephone has passed the certificate of ISO9000(2000) 12.size:according to customer's request.