Abstract: An electronic system for incorporation in a racquet that monitors a player's ability to hit balls within a specific region on the string bed. A plurality of sensors are positioned around the periphery of the racquet string bed for detecting the relative time-of-arrival of transverse waves produced by impacts of balls on the string bed. A circuit incorporated within the racquet receive the signals from the sensors and provide a plurality of signals from which the position of impact on the string bed may be calculated. The system incorporates a low power microprocessor that is programmed to compute the ball impact location from the signals produced by the sensors. A display device on the racquet displays information derived from the calculated impact location to permit players to assess their performance as related to hitting a predetermined region.

Abstract: The present invention generally relates to a system for use in determining the location and orientation of concealed underground objects and, more particularly, to an improved locator system having a unique and improved interface with an operator. In accordance with one embodiment of the invention, a magnetic field detector for locating concealed underground objects is provided. The magnetic field detector includes a housing having an upper housing portion and a lower housing portion. A receiver is disposed within said housing for receiving magnetic field signals from the concealed underground objects. A swivel joint couples the upper housing portion and the lower housing portion to permit relative rotational motion.

Abstract: An improved locator system is provided which simultaneously couples a number of different frequency signals to a number of concealed underground conductive lines, for the purpose of locating and distinguishing between the underground lines. The locator system includes a transmitter which generates the different frequency signals for coupling to the underground lines. A receiver is also provided that detects the different frequency signals and distinguishes between the underground lines. The locator system further provides an arrangement for operating at virtually any frequency within the locating band, and for preselecting an operating frequency that avoids interference from extraneous signals.

Abstract: The present invention generally relates to a system for use in determining the location and orientation of concealed underground objects and, more particularly, to an improved locator system having a unique and improved interface with an operator. In accordance with one embodiment of the invention, a magnetic field detector for locating concealed underground objects is provided. The magnetic field detector includes a housing having an upper housing portion and a lower housing portion. A receiver is disposed within said housing for receiving magnetic field signals from the concealed underground objects. A swivel joint couples the upper housing portion and the lower housing portion to permit relative rotational motion.

Abstract: An automatic telephone number dialing service for use with mass-distribution media products to enable consumers to automatically dial a preprogrammed number associated with one or more sources of goods and/or services. The device may be constructed as an insert for, or attachment to, various media such as magazines, books, direct mail advertising, newspapers and the like. The device may also be constructed as a customized service card for accessing sources of products or services. The preprogrammed number may be that of a centralized, automated, or personal telemarketing system. The dialing device includes a single chip microprocessor capable of producing DTMF tones corresponding to the preprogrammed telephone. By passing the tones through a miniature speaker or other sound transducer, the preprogrammed number will be automatically dialed. A related telemarketing process using the device is also disclosed.

Abstract: An improved phase-locked loop includes a phase detector, active loop filter and a VCO, in conventional phase-locked loop relationship. In addition, a positive feedback path couples active loop filter output to active loop filter input. In the absence of loop lock, the positive feedback provided by the positive feedback path satisfies the conditions necessary for the production of an oscillating output from the active loop filter circuit. The oscillating output generated by this "oscillator" drives the VCO in a sweeping action allowing the loop to acquire signals outside of its normal capture range. On capture, phase detector output provides an additional negative feedback path which overrides the effect of the positive feedback path and therefore, oscillations cease and the loop locks. The positive feedback path can comprise a relatively simple passive frequency selective circuit.

Abstract: A direction phase shift keyed communication system provides the capacity to transmit any one of two symbols for each modulation level. The modulator produces a substantially constant frequency signal which includes a phase transistion in respect of each information bit. In a system with a single modulation level, corresponding to a phase transistion .phi., one of the two symbols is represented by a phase transition +.phi., i.e., an advancing phase transition. The other symbol is represented by a phase transition -.phi., i.e., a retarding phase transition. A demodulator responds to a substantially constant frequency signal with a phase transition included, and produces an output signal of a first kind in response to an advancing phase transition +.phi. and an output signal of a second kind in response to a retarding phase transistion -.phi.. The system is capable of operating with multiple modulation levels, each of which can represent any one of two symbols, depending on the sense, i.e.

Abstract: A phase-locked demodulator for demodulating a phase-difference modulated carrier having a repeated phase offset increment introduced therein. The demodulator includes, in common with conventional phase locked demodulators, a mixer having a first input connected to receive the modulated carrier and a reference carrier generator such as a voltage controlled oscillator (VCO) connected in a phase-locked feedback loop forming the second input to the mixer. In order to reduce the number of output levels, the VCO is tuned to a frequency Fr=Fc.+-.Fb[(.alpha.)/360] where Fc is the carrier frequency, Fb is the baud rate and .alpha. is the repeated phase offset. In this way the phase offset increment introduced into the modulated carrier is substantially cancelled out thereby leaving only the phase changes containing data information.