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1964 - new system of voice communication via a light beam


CD 2055070 E&MP7.008 and 7.009


19 April 1964

NASA has developed a new system of voice communication via a light beam.

The Retrometer is so-called because the light beam over which voice signals are sent is returned directly to its source by a corner reflector.

It consists of three major functional parts: a light source, a corner reflector, and a light-collection system.

The light source and light-collection system are in one unit, left. The corner reflector -- which acts as a microphone -- is a passive modulator, requiring no power except the human voice.

additional text found 1964 - new system of voice communication transmitted on a beam of light

April 19, 1964


A new system of voice communications transmitted on a beam of light was revealed today by the National Aeronautics and Space Administration.

The system differs from previous ones in that the originating station requires no power other than the human voice.

And the NASA Retrometer is believed to be alone among light beam communications systems in offering a simple, convenient, and inexpensive device at one terminal.

The Retrometer - so-called because the light beam over which voice signals are sent is returned to its source by a simple reflector - was devised at NASA's Langley Research Center, Hampton, Va.

A Langley researcher, Numa E. Thomas, developed the Retrometer while investigating optical methods of communications between the ground and a re-entry vehicle during the radio blackout period.

The discovery was revealed in a technology Utilizations Report issued by NASA's office of Technology Utilization.

The T-U Reports are detailed descriptions of space technology innovations with high potential for non-space use.

T-U has set up and maintains a steady flow of technical information from the nation's space program to private industry.

In the new Report, T-U points out that successful development of systems based upon the Retrometer principle might find use in many areas.

Among commercial applications are: surveying, use in construction work (particularly where radio transmissions are hampered by steelwork and tunnels of prevented by blasting); use in steel mills and other plants where high level noise is a problem; communications during special events, political conventions, and emergency situations, including forest fires, shipwreck and other disasters.

Other possible applications are air-sea operations, air-to-sea, ship-to-ship, and ship-to-shore communications, air-refueling operations, and tactical communications.

Among its space applications are rendezvous and docking of spacecraft, emergency communications, and ground-to-gantry communication.

The T-U Report cites dozens of other possible uses for the Retrometer.

The Report is listed as NASA SP-5005 and is on sale for 50 cents by the office of Technical Services, Department of Commerce, Washington, D.C. 20230.

The Report gives instructions on how experimental Retrometers can be constructed in any small electronics and optical shop.

Many of the device's details are noncritical and can be varied according to need and facilities.

The complete Retrometer system consists of a battery case, the source/receiver unit and the corner reflector.

Five 1.35 mercury cells power the light source and a 9-volt battery powers the transistorized amplifier.

A four wire cable and plug connect the power pack to the source/receiver unit.

Immediate commercial use of this invention, which is owned by the Space agency is encouraged by NASA under royalty-free, non-exclusive licenses.

Inquiries about license rights should be made to the National Aeronautics and Space Administration, Code AGP, Washington, D.C. 20546. 

Original Caption by Science Service

National Museum of American History


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