The Howl Call Telephone is a sound powered device with highly efficient dynamic transmitter and receiver capsules offering communication without power supply. The call signal is generated by turning the rotary knob with an audio frequency dynamo. These telephones are made with extremely sturdy, impact-resistan and weatherproof housing. The Howl Call Telephone has proven its worth in years of operation in mining, tunnelling, building sites and industrial operations. The approximate range is 10km.