Abstract: In a frequency-domain excision system for a wide band receiver, a window function is applied to blocks of received signal samples and a transform function is applied to the windowed blocks. Each block of frequency-domain coefficients from the transform function is morphologically filtered to generate a threshold function representing an estimate of the spectrum of the desired wide band signal, and a non-linear gain function is applied to the coefficients. The gain function has a fixed-gain region for input values less than a threshold value from the threshold function, an excision region for input values greater than a multiple of the threshold value, and a soft limiting region between the fixed-gain region and the excision region. The inverse transform is performed on the excised blocks of coefficients, and an overlap-eliminating central portion of the inverse of the window function is applied to the resulting blocks of signal samples.

Abstract: In an encryption system, a serial data stream is demultiplexed into a plurality N of encryptor input data streams to form a sequence of encryptor input data slices applied to an encryptor having a cascade of stages. Each stage includes a mapping function and a delay function, the mapping function performing a stage-specific direct mapping of data slice values to corresponding generally different data slice values, and the delay function applying stage-specific and generally different delays to individual symbols of data slices. Encrypted data slices generated by the last stage of the encryptor are transmitted through a transmission channel and received at a decryptor having a cascade of stages. Each decryptor stage includes an equalizing delay function and an inverse mapping function to generate output data slices from input data slices.

Abstract: A novel method and apparatus encodes a data signal (e.g., before wireless transmission) such that the encoded signal has Gaussian statistics and the transmitted signal exhibits virtually no signal structure. This approach represents a significant improvement over previous attempts, as no synchronization between the encoder and decoder is required and the linearity of the transfer channel is preserved. Implementations of systems, methods, and apparatus according to embodiments of the invention are disclosed wherein the encoded signal has a flat power spectrum, wherein different codes are assigned to different users, wherein compensation for phase shifts is performed, and wherein the design and/or construction of the implementation may be accomplished using various digital filtering architectures.

Abstract: In a frequency-domain excision system for a wide band receiver, a window function is applied to blocks of received signal samples and a transform function is applied to the windowed blocks. Each block of frequency-domain coefficients from the transform function is morphologically filtered to generate a threshold function representing an estimate of the spectrum of the desired wide band signal, and a non-linear gain function is applied to the coefficients. The gain function has a fixed-gain region for input values less than a threshold value from the threshold function, an excision region for input values greater than a multiple of the threshold value, and a soft limiting region between the fixed-gain region and the excision region. The inverse transform is performed on the excised blocks of coefficients, and an overlap-eliminating central portion of the inverse of the window function is applied to the resulting blocks of signal samples.

Abstract: A personal alarm system is disclosed which incorporates a speakerphone so as to permit substantially handsfree operation and remote activation. The system includes a speakerphone which interfaces to a subscriber station. The subscriber station in turn interfaces over a communications link to a central monitoring station which is operative to receive and analyze messages transmitted to the central monitoring station by the subscriber station. Following transmission of a message from the subscriber station to the central monitoring station, the central monitoring station may transmit a control signal to the subscriber station which causes the subscriber station to activate the speakerphone to permit verbal communication with a subscriber who may be immobilized and/or physically unable to initiate a telephone call or answer a telephone.

Abstract: A novel alarm system tester is disclosed for use in verifying the operation of subscriber stations in an alarm system of a type having a central monitoring station and a plurality of subscriber stations operative to automatically dial the telephone number of the central monitoring station and to report the occurrence of an alarm event to the central monitoring station. The tester in accordance with the present invention permits the verification of the automatic dialing function of the subscriber station and additionally, provides for verification that the subscriber station can transmit messages to the central monitoring station in accordance with a defined communication protocol. The entire test sequence is completed in a single telephone communication.

Abstract: An emergency response system in which the low battery condition of a wireless help unit is automatically detected and indicated at a receiver. The help unit provides, as part of the transmitted signal, a signal indication of battery condition. The received signal is decoded and, upon detection of a low battery signal indication, a visual and/or audible output indication denotes this condition. The low battery indication at the receiver remains on until a transmission is received from the help unit when containing a fresh battery replacement.