Editing Telephone (section)

=== Principle of operation ===
A moving-coil microphone converts the sound waves into an electrical signal, which is then converted back into sound waves at the receiver's end. Similar to early regular landline telephones, operators of sound-powered telephones generally alert the receiver of a call using a hand-cranked generator (magneto), which generates an electrical current which activates a buzzer at the receiver's end, sometimes known as a howler or growler. Some telephone systems can use external electrical power to operate ringers or amplifiers, but will revert to sound-powered communications in the event of failure of the external power supply.<ref name="NavElec">{{cite web |title=Products: Civil Vessels Telephone: Sound Powered Telephone |url=https://www.navelec.com/products/civil-vessels-telephone/sound-powered-telephone/ |website=NavElec |publisher=NavElec consortium |access-date=10 December 2024 |url-status=live |archive-date=23 April 2024 |archive-url=https://web.archive.org/web/20240423202316/https://navelec.com/products/civil-vessels-telephone/sound-powered-telephone/ }}</ref> Stations are usually connected via [[twisted pair]] wires to reduce electrical interference, and can be positioned at considerable distances from each other in the order of several kilometers. Using 1mm core diameter twisted-pair wiring, some sound-powered telephone systems can operate a pair of handsets positioned up to 48&nbsp;km (30 miles) apart.<ref name="Dynalec FAQ">{{cite web |title=Sound Powered Telephone: Frequently Asked Questions |url=http://soundpoweredtelephone.com/sound-powered-frequently-asked-questions.html |website=Sound Powered Telephone |publisher=Dynalec Corporation |access-date=10 December 2024 |archive-url=https://web.archive.org/web/20241210120847/http://soundpoweredtelephone.com/sound-powered-frequently-asked-questions.html |archive-date=2024-12-10 |date=2011 |url-status=live}}</ref>