A special-purpose communications subsystem provides a push-to-talk signal to a communication system as if the individual was directly wired to the system. The subsystem also permits multiple wireless users to operate independently in the same environment. This interface operates in the 900-MHz industrial, scientific, and medical (ISM) frequency band and can be used with many different commercial off-the-shelf (COTS) wireless-communication headsets, without need to modify the headsets or the communications system in use.

The Keying Transmitter, which is shown here separate from the transmitter of the headset, sends the push-to-talk signal to the auxiliary receiver at the base station.

COTS wireless-communication headsets operate continuously (transmit and receive), without the need for push-to-talk signaling, and are not designed to provide any special signaling like a push-to-talk signal or external "off hook" "on hook" signals. In the original application for which the present interface was developed, there is only a requirement for push-to-talk signaling to activate and deactivate users participating in launch operations via a COTS communication system. Similar communication systems are in use by Department of Defense agencies, law enforcement and public safety (including 911) call centers, other mission critical communications environments, and even commercial (telemarketing) call centers.

The interface has been prototyped, is in use for launch operations, and includes a push-to-talk unit carried by each headset wearer. This is a low-power auxiliary radio transmitter and is in addition to the radio transmitter of the headset. The interface could, however, be licensed for direct integration into COTS wireless headsets by the manufacturers, and could be expanded to perform a variety of specialized telephony functions, like DTMF (dual-tone multiple frequency) delivery, and on/off hook signals. The interface also includes an auxiliary radio receiver at the base station. When a wearer intends to transmit, the wearer keys the push-to-talk unit. Upon detecting the signal from the auxiliary transmitter, the auxiliary receiver at the base station generates a control signal equivalent to a conventional wired push-to-talk control signal. In the application that was prototyped, the control signal is one that commands the closure of a switch to turn on the audio circuits in the base station.

This work was done by Marc Seibert of Glenn Research Center and Anthony J. Culotta of Boeing for Kennedy Space Center. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp  under the Electronics & Computers category.

This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to

the Technology Programs and Commercialization Office
Kennedy Space Center
(407) 867-6373.

Refer to KSC-12052.

NASA Tech Briefs Magazine

This article first appeared in the January, 2001 issue of NASA Tech Briefs Magazine.

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