How do sound powered telephones work?

Sound powered telephone communication technology uses electro-mechanical transducers to provide audio communication over a single wire pair without the use of external power or batteries. The sound pressure produced when a user talks into the handset/headset transmitter generates a voltage that is sent to the receiver which converts it back into sound. And that is all that is required to power the system.

A sound powered telephone network is often the only means of communication available during power failures and is thus hailed as a critical communication link during casualty or stealth conditions. As an example, a study of the attack on the USS Cole in October 2000 concluded that it was a major mistake to not have full sound powered telephone systems as they did on earlier ships. The Cole lost all power - and all communications - during the attack except their sound powered telephone system. It became their main, and only, communications channel.

Sound powered telephones are also used for temporary and permanent communications systems in many industrial and commercial applications:

• airports
• fire and police rescue crews
• public utilities
• schools
• vaults
• subways
• refrigeration plants
• civil defense
• bridge installations
• ski slopes
• oil fields
• parks and forest
• railroads
• salvage yards
• sporting arenas
• shipyards
• diving projects, and
• geophysical operations where power is not available.

Sound powered telephone equipment operates at low voltage levels. This makes it ideal for arsenals and powder works, gas works, chemical plants, oil refineries, mines and quarries, ballistic missile sites, nuclear installations – or any environment requiring “explosion proof” equipment.

Lightweight, portable, and weatherproof, sound powered equipment is comfortably used for in-plant and outside maintenance, construction and repair, electrical contract installations, public utilities, radio, television, telephone installations and shipboard operations.