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 hybrid data frame is presented for a time division multiple access frequency hopping communications system. The frame includes uplink and downlink subframes, and each subframe includes a plurality of frequency hops. First frequency hops in each subframe have at least one time slot, and the first hops follow default non-adaptive frequency hopping patterns, such that unsynchronized communicating units can synchronize with the communications system during the first hops using the predetermined default pattern. The second frequency hop also includes at least one time slot, and employs an adaptive frequency hopping pattern. Once a communicating unit is synchronized to the communications system via the first frequency hop, it can be assigned to a time slot within the second hop and adaptive frequency hopping interference avoidance techniques can be implemented.

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: A digitally implemented demodulator. A frequency-modulated signal is applied to a limiting amplifier such that the signal amplitude is fixed at a constant level. The signal is undersampled and quadrature demodulated. The demodulator generates the cross-product of the baseband complex envelope to recover the original modulating signal. A digital Frequency Shift Keyed signal can be further recovered by applying the recovered signal to a data slicer to square-up the signal, and a matched filter for improved error resistance.

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 cordless telephone headset, which is controlled by an unattached handheld control module. The control module includes a keypad, and emits an infrared signal towards the user's head corresponding to the depression of a particular key on the keypad. The cordless headset is worn on a user's head, receives the infrared signals originating from the control module, and performs a function corresponding to the particular signal received, such as dialing a number or placing the telephone on hook. The control module includes a visual display screen that provides visual confirmation of keypad depressions. The control module also displays caller identification or other data for visual observation.

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 two-axis ball-based cursor control apparatus with tactile feedback is provided, which includes a housing, a spherical ball contained partially within the housing, a plurality of magnetic elements fixed within the spherical ball, and a plurality of magnetic elements fixed within the housing. When the spherical ball is at rest, an attractive magnetic force between some or all of the first magnetic elements and some or all of the second magnetic elements resists motion of the ball. When a sufficient rotational force is applied to the ball, the ball rotates about one or both axes until the applied force no longer exceeds the magnetic force, at which point the magnetic force causes the ball to stop at a new position, providing the user with tactile feedback to indicate that the ball position has changed.

Abstract: An error monitor for indicating the quality of communications on a digital communication channel. One or more error detection mechanisms provide indication when an error occurs. After receipt of an error indication, no further indications are detected until a burst error time window has passed. Error indications are stored in a bin. When time since an error indication has been received exceeds a second time period, the event is removed from the bin. When all slots in the bin contain error indications, an indication of the quality of communications on the channel is provided. Parameters can vary with the strength of the received signal to accommodate long range conditions.

Abstract: The present disclosure discloses a method and apparatus for slicing data, or “squaring up” a signal such as the output of a wireless receiver demodulator for proper interface with conventional digital logic circuits. The method involves the receiving of an input signal, the generation of a reference level, the comparison of the input signal to the reference level, and the measurement and storage of the reference level. The reference level is generated by applying the input signal to a filter, which has been previously set to an initial condition. The reference level is measured at a predetermined point in a receive data frame, and is maintained at the desired level throughout the remainder of the frame. After a frame has been received, the reference level is stored if the frame data output from the data slicer contained no errors.

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: The disclosure discloses a method for extending the length of time over which a cordless telephone system can operate without an external source of power. The method involves detecting a power supply outage, determining that a telephone call is not currently being handled, placing the portable unit into a mode of reduced power consumption, and placing the base unit into a mode of reduced power consumption. After a period of time, the base unit resumes functionality, determines whether a call is being initiated, and handles any such calls. If the system is not active, the base unit re-enters its mode of reduced power consumption, and the cycle is repeated.