Harris Corporation

Robert D Talbot

Donald R Martz

A transmission line balun comprising a tubular ferrite having a longitudinal passageway concentrically positioned over a conductive sleeve having a longitudinal passageway. The end of a coax feeder is positioned in the longitudinal passageway of the sleeve and the sleeve is grounded at its proximal end to the shield of the coax cable. The sleeve buffers the effects of the parasitic line caused by using ferrite in a balun.

Transmission line balun for broadband combiners, splitters and transformers

A method and circuit for detecting and reducing the impedance mismatch between the directional coupler and the antenna of an RF communications system exposed to externally generated RF signals. The impedance mismatch is detected by the quadrature multiplication of the signal passing through a directional coupler in the forward and reverse directions with the detection being enhanced by the use of a forward direction signal substantially devoid of externally generated RF signal components.

Tuning method for automatic antenna couplers

A circuit for reducing the effect of acoustic and electrical feedback in duplex 'hands free' telephone sets. The circuit uses relatively simple and inexpensive gain control circuits and expanders to reduce the effects of feedback by controlling the gain of a transmitted signal in inverse relationship to the strength of a the received signal.

Duplex hands-free communications circuit

A communications system including a central station and a plurality of remote stations, for example, a mobile telephone system, is disclosed in which communications channel establishing signalling transmissions between the central and remote stations are conducted in a clear (unenciphered) mode and subsequent voice transmissions between the central and remote stations are conducted in a secure (enciphered) mode. Each remote station has a unique code assigned thereto which is used by it to at least decipher incoming enciphered voice transmissions from the central station and by the central station to encipher outgoing voice transmissions to the remote station. The unique code may also be used by the remote station to encipher outgoing voice transmissions and by the central station to decipher incoming voice transmissions from the remote station. Alternatively all remote station outgoing voice transmissions may be enciphered with a code common to all remote stations which code is used by the central station for deciphering incoming voice transmissions. The central station can automatically, or in response to a specific request for secure service, switch its equipment to the secure mode upon completion of communications channel establishing signalling transmissions between it and a remote station and can control remote station switching to the secure mode by sending an enciphered voice transmission to the remote station which responds to receipt thereof by switching to the secure mode.

Secure mobile telephone system

A communications system including a central station and a plurality of remote stations, for example, a mobile telephone system, is disclosed in which communications channel establishing signalling transmissions between the central and remote stations are conducted in a clear (unenciphered) mode and subsequent voice transmissions between the central and remote stations are conducted in a secure (enciphered) mode. Each remote station has a unique code assigned thereto which is used by it to at least decipher incoming enciphered voice transmissions from the central station and by the central station to encipher outgoing voice transmissions to the remote station. The unique code may also be used by the remote station to encipher outgoing voice transmissions and by the central station to decipher incoming voice transmissions from the remote station. Alternatively all remote station outgoing voice transmissions may be enciphered with a code common to all remote stations which code is used by the central station for decipering incoming voice transmission. The central station can automatically, or in response to a specific request for secure service, switch its equipment to the secure mode upon completion of communications channel establishing signalling transmissions between it and a remote station and can control remote station switching to the secure mode by sending an enciphered voice transmission to the remote station which responds to receipt thereof by switching to the secure mode.

Growing community of inventors

Pittsford, NY, United States of America

Robert D Talbot