Abstract: A technique for time domain avoidance of communications link interference sources characterized by intermittent, periodic short bursts of energy. A transmitting source can be assigned two time slots within a time domain multiple access data frame over which each data packet can be transmitted. The time slots are separated by a duration greater than that of an interference burst, such that an interference burst does not affect both time slots in any given frame. Therefore, the data packet can be received on at least one of the two assigned time slots. Transmitter power consumption can be reduced by calculating the timing of the periodic interference bursts, and only transmitting a data packet on one of the two assigned time slots that will not coincide with an interference burst in each frame. Communications link capacity can be improved during the presence of interference by synchronizing the data frame to the timing of the interference bursts.

Abstract: A technique for time domain avoidance of communications link interference sources characterized by intermittent, periodic short bursts of energy. A transmitting source can be assigned two time slots within a time domain multiple access data frame over which each data packet can be transmitted. The time slots are separated by a duration greater than that of an interference burst, such that an interference burst does not affect both time slots in any given frame. Therefore, the data packet can be received on at least one of the two assigned time slots. Transmitter power consumption can be reduced by calculating the timing of the periodic interference bursts, and only transmitting a data packet on one of the two assigned time slots that will not coincide with an interference burst in each frame. Communications link capacity can be improved during the presence of interference by synchronizing the data frame to the timing of the interference bursts.

Abstract: A reliable data communications protocol for the broadcast of long messages over a noisy medium, such as a frequency hopping communications link with multiple interferors. Long length messages are divided into a plurality of subpackets, each of which incorporates an error detection mechanism. A message integrity field is calculated based upon the contents of the subpackets, and is stored within one of the plurality of subpackets. The subpackets are transmitted two or more times. Each subpacket is stored by a recipient if received without error, and the recipient calculates a message integrity field based upon the stored subpackets. When the calculated message integrity field corresponds to the message integrity field received within the subpackets, the long message is deemed properly transmitted, reassembled from the plurality of subpackets, and processed appropriately.

Abstract: A low-power sleep mode of operation for a frequency hopping radio receiver is presented. Digital circuits within the receiver operate based upon a high frequency clock source. During sleep mode, the circuits are clocked with a low-frequency clock source, which is typically less accurate in frequency. Periodically, the receiver awakens. The hop sequence channel tuned by the receiver is determined by a mapping based upon the channel upon which the receiver expects to receive communications. The mapping can be changed as necessary to improve tolerance to timing error. Furthermore, once communications are received after a sleep period, the frequency error of the low-frequency clock source can be determined, and compensated for after awakening from subsequent sleep periods.

Abstract: A technique for controlling the frequency allocation in the hop sequence of a frequency hopping digital communications system is presented. The hop sequence is initially formed such that consecutive channels are likely to differ substantially in frequency. Therefore, channel substitution commands can be transmitted twice on consecutive hops without acknowledgement, inasmuch as the likelihood of a broadband noise source blocking consecutive channels is reduced. The number of channels identified as requiring substitution in the hop sequence is monitored, such that a hop sequence repair operation or communications link termination can be implemented if channel substitution data traffic becomes too great.

Abstract: A technique for time domain avoidance of communications link interference sources characterized by intermittent, periodic short bursts of energy. A transmitting source can be assigned two time slots within a time domain multiple access data frame over which each data packet can be transmitted. The time slots are separated by a duration greater than that of an interference burst, such that an interference burst does not affect both time slots in any given frame. Therefore, the data packet can be received on at least one of the two assigned time slots. Transmitter power consumption can be reduced by calculating the timing of the periodic interference bursts, and only transmitting a data packet on one of the two assigned time slots that will not coincide with an interference burst in each frame. Communications link capacity can be improved during the presence of interference by synchronizing the data frame to the timing of the interference bursts.

Abstract: A cordless telephone implementing using a BLUETOOTH wireless bearer is presented. A BLUETOOTH voice data structure is implemented by coding the voice data at a bitrate below 64 kb/s, such that the full number of payload bits provided by the BLUETOOTH voice data structure are not required for transmission of voice data. The packet payload is then encoded in a non-standard format to implement a robust error detection and/or correction protocol for the voice data, as well as for the provision of a low-rate data channel for transmission of information such as caller ID. Alternatively, a BLUETOOTH non-voice data structure can be employed by transmitting encoded voice data as user payload bits. The data link is then flushed each time new voice data is ready for sending by the transmitting device. If slots are available before the data link is flushed, unsuccessfully transmitted data can be automatically resent, thereby implementing time and frequency diversity.

Abstract: A digital circuit for driving an audio transducer that provides consistent tonal quality over a range of volume levels, without requiring a variable gain analog amplifier. A fixed amplitude ringer tone is multiplied, or amplitude modulated, by a higher frequency digital pulse train to produce a transducer driving signal. The timbre of the transducer driving signal is similar to that of the fixed amplitude ringer tone, but the volume of the sound produced by the transducer varies with the mark-space ratio of the pulse train.

Abstract: The present disclosure discloses a method and apparatus for detecting and preventing telephone call fraud. The call fraud detector apparatus is connected to the telephone line, and includes a telephone line interface with switch hook. A parallel set detector indicates to the microcontroller that another device has gone off hook on the telephone line. The microcontroller causes the telephone line interface switch hook to also go off hook in parallel, thereby preventing pulse dialing by the other device. The device may also include a DTMF tone detector and generator to prevent DTMF dialing on the telephone line. The call fraud detector can provide a visual, audible, and/or tactile indication when unauthorized use of the telephone line occurs, and can be enabled or disabled by an external device. The call fraud detector can log the time and date of each unauthorized call placed on a line, and can also notify the telephone service provider when an unauthorized call is attempted.

Abstract: An apparatus for synchronizing the system clocks of wireless devices in a digital communications system is presented. A digital phase-locked loop is employed. The phase-locked loop may include a counter which is incremented by a local device system clock and latched by a frame synchronization marker received from a remote device, whereby the counter output comprises a feed forward signal. The phase-locked loop may alternatively include a counter that reflects the level of data stored in receive and/or transmit FIFO buffers. The loop output signal controls the frequency of the system clock oscillator.

Abstract: A two-axis ball-based cursor control apparatus is provided, which includes a housing; a spherical ball contained partially within the housing; two rotors in contact with the spherical ball and two corresponding axles; two screw devices associated with each rotor-axle pair, each screw device having a continuous helical thread; a plurality of light sensors, each associated with a screw device; and a means for processing the signal from the light sensors. When the spherical ball is rotated by the user, its motion about each axis of rotation is translated to one of the screw devices by means of the corresponding rotor-axle pair. The rotation of the screw devices causes the helical thread on each to momentarily interrupt the light beam generated by each sensor at least once during each revolution of the screw device, thereby generating a signal which is translated into two-dimensional motion of a cursor on an electronic display screen.

Abstract: A touch screen overlay apparatus for use in association with a touch screen having a rigid contact surface. The touch screen overlay apparatus comprises a flexible membrane that covers at least a portion of the rigid contact surface. This flexible membrane is removably maintained in a predetermined position over the rigid contact surface to provide a more tactually desirable surface for manual actuation than the rigid contact surface. Furthermore, the flexible membrane may include one of said one or more raised dome-shaped regions which are disposed on the membrane so as to be in substantial registration with input regions on the rigid contact surface to provide tactile landmarks for the user.

Abstract: A phase-locked loop controller for a frequency hopping communications system which utilizes an indirect addressing scheme to access PLL data is provided. The controller is hardware-implemented, with little or no microcontroller processing overhead required. The controller enables simple synchronization with other units in a communications infrastructure implementation. The controller provides a simple interface for implementing dynamic channel allocation methods. An override port allows external control of the PLL with which the controller is associated. Finally, the controller can control auxilliary aspects of system operation, such as powering down a transmitter while changing PLL tuning.

Abstract: The present disclosure discloses an apparatus for generating a shaped waveform derived from a binary input signal. The apparatus receives a binary input signal and a sample clock signal. The sample clock signal changes the state of an up/down counter. The binary input signal controls the counting direction of the counter. The counter addresses a lookup table containing stored values. Also disclosed is the apparatus in which the lookup table output is converted to an analog signal by a digital-to-analog converter. The lookup table can be programmed such that the circuit output is equivalent to a filtered version of the binary input signal. The apparatus may optionally be enabled or disabled, such that the apparatus output assumes a predetermined state when disabled.