Abstract: A sports mat system incorporating a reversible thermochromic leuco dye includes an impact pad portion having a reversible thermochromic leuco dye incorporated into it in order to provide a temporary visual indication of the path of a sports apparatus swing. The impact portion changes color with a temperature change due to frictional contact between the pad and the equipment being swung, in order to visually illustrate the swing path of the club along with the club head/face orientation during impact. In another implementation, a racquet is provided incorporating a reversible thermochromic leuco dye into a portion of racquet strings to temporarily visually illustrate the contact area between the racquet face and a ball being struck, in order to provide the user with feedback relating to characteristics of their swing.

Abstract: The present invention relates to a means for achieving simultaneous transmission of data and speech with only a minimal expansion of the bandwidth of the speech signal. A Fourier transform (14) is performed on the speech signal and a predetermined number of phase components are replaced with data (d(n)) in an appropriate form. The number of phase components replaced with data is determined by approximately classifying the speech (16) as either "silence", no data inserted; "unvoiced" speech, M phase components convey data; and "voiced" speech, J phase components convey data; where J is less than M, and M is not greater than the number of phase components in the message band of the speech signal. An inverse Fourier transform (22) is subsequently performed on the combined data and speech signal. The combined message signal (G(t)) will comprise approximately the same bandwidth as the original speech signal, by virtue of the frequency domain insertion of the data into the speech.

Abstract: The present invention relates to a frequency-hopped single sideband (SSB) mobile radio system implemented by hopping the carrier frequency of an input signal (s(t)) every .tau. seconds. The hopping is controlled by a carrier-frequency-hopped sequence (f.sub.i (t)) generated by a carrier-frequency-hopping generator (16,24). When employed in a frequency-hopped SSB transmitter (10), the carrier sequence functions to modulate the input signal, "hopping" it to a different carrier frequency every .tau. seconds. The carrier-frequency-hopped SSB receiver (20) employs the identical carrier sequence as used by the transmitter to demodulate the transmitted carrier-frequency-hopped SSB signal, thereby recovering the original single sideband signal (s(t)). By frequency hopping the carrier signal of an SSB signal, the present invention mitigates the effects of co-channel interference and frequency selective fading inherent in prior art SSB cellular mobile radio systems.

Abstract: In its most general form, the present invention may be employed to simultaneously transmit information, either digital or analog, from two separate and distinct sources, denoted A and B, where the information from at least one of the sources, for example, A, possesses some known statistical properties of coherence. The less coherent information from, for example, source B, is used to generate a set of scrambling key sequences, where each separate scrambling key sequence is associated with a unique segment of information from source B. The key sequences are used to scramble the information from source A, and the scrambled information is produced as the output of the transmitter. In one form, the information from source A could be an analog signal (x(t)) and the information from source B could be a digital data sequence ({d.sub.k }) which is capable of transmitting n data bits per every N samples of the analog signal from source A.

Abstract: The present invention relates to a secure communication system for analog signals which preserves the bandwidth of the original message signal by employing scrambling, or masking, techniques in the frequency domain instead of the time domain. At the transmitting end, the message signal x.sub.a (t) is sequentially passed through a Fourier transform processor (12) and a scrambling arrangement (14) before being masked to form a secure Fourier transform sequence X.sub.s (n). The secure message signal x.sub.s (t) is formed by passing the secure sequence X.sub.s (n) through an inverse Fourier transform processor (16) which produces a secure signal x.sub.s (t) comprising the same bandwidth as the original message signal x.sub.a (t). At the receiving end, the secure signal x.sub.

Abstract: An arrangement reduces transmission errors in a communication system that includes a transmitter operative to convert an input signal into blocks of coded signals and a receiver operative to convert the coded blocks into a replica of the input signal. In the transmitter, a signal representative of first features of the input signal and a signal corresponding to second features of the input signal are generated. In the receiver, corrupted received coded signals are detected responsive to the first feature signal and the received blocks of coded signals. Each corrupted received coded signal is modified jointly responsive to the received blocks of coded signals and the second feature signal to reduce errors in the input signal replica.

Abstract: An error reducing arrangement is provided for a signal receiver wherein a sequence of received signals is divided into groups and each group is partitioned into subgroups. A signal representative of the deviations among the signals of each group and a signal representative of the deviations among the signals of each subgroup of said group are generated. Responsive to a subgroup deviation signal exceeding its group deviation signal, the subgroup signals are altered to reduce the subgroup deviations. In this manner errors are reduced without affecting error free signals.