Abstract: A mobile communication system and a control method in which a line controller controls speech channels to be used by fixed transceivers. The line controller is coupled to wired telephone lines, and to a plurality of fixed transceivers. The fixed transceivers are coupled to mobile transceivers by radio circuits. The line controller stores the status of available speech channels, and when there is an incoming call on one of the telephone lines or thre is an outgoing call from one of the mobile transceivers, informs one of the fixed transceivers of the status of a set of speech channels. The fixed transceiver subsequently selects one of the set of speech channels, and informs the line controller of its selection so that the status of the speech channels can be updated.
Abstract: An echo cancellation modem having a fast training echo canceller in which the echo cancellation coefficients are computed by taking correlations between a complex, periodic training signal sequence and a real component of the corresponding echo signal. The modem includes a receiver circuit for detecting a signal on a channel possibly including an echo; an echo canceller for estimating the real component of the echo signal; training circuitry for applying the complex training sequence to the channel and for taking correlations between the training sequence and the real component of the corresponding echo signal. The modem also includes a computational element for computing the period of the periodic sequence, generating the complex periodic train sequence in real time and for computing a phase roll frequency based upon the computed echo cancellation coefficients.
Abstract: An automatic dialing apparatus stores in a RAM an area code number, a local code number and a plurality of subscribers' telephone numbers in the area of the local code number thereof with hyphens for separating these numbers and telephone numbers from each other. It further displays a series of telephone numbers on a display portion in the apparatus in response to operation of a search key. When a local key is operated, a local code mark is detected, a local code number of digits higher than the local code mark is cancelled, and thus the telephone numbers of digits lower than the local code mark are displayed. Each time the local key is operated, the hyphens in the telephone numbers are searched for to be displayed. If a dial out key is operated when a desired telephone number is displayed, a tone signal corresponding to the desired telephone number is generated. Therefore, an arbitrary number can be selected from a series of numbers.
Abstract: The disclosure concerns digital telephone sets and, more particularly, those with amplified listening facility and "hands free" telephones. To fulfil the function of the anti-Larsen effect needed in these telephones, there is need for a signal envelope detector which gives a measurement of the mean level of the signal emitted or received on the line. According to the disclosure, the cofidec present in the digital telephones is used to establish an envelope detection system with logarithmic compression. This removes the need to do a logarithmic detection on the analog speech signal. Such a detection would necessitate diodes, upside down with respect to each other, which can be made, particularly, only through bipolar technology. A series/parallel converter, a digital comparator and a counter having a countdown frequency which is far slower than the counting frequency, fulfils the signal envelope detection function.
Abstract: In an arrangement for simultaneously exchanging digital symbols between terminals over a bidirectional transmission path, near term interference in the signal received from the transmission path is canceled by storing the sequence of successive digital symbols 1, 2, . . . , N applied to the transmission path, forming a replica of the interference from the stored digital symbols and subtracting the replica from the received signal. A signal representative of a replica of the interference occurring subsequent to the Nth digital symbol of the successive digital symbols 1, 2, . . . , N is then generated and combined with the signal having the interference corresponding to the stored symbol sequence removed to cancel the subsequent interference in the received signal.
Abstract: An adaptive speakerphone employs an echo suppression arrangement which compensates for a reverberant effect that occurs during operation of the speakerphone in a near full or full duplex mode. This reverberant effect allows the far-end party to hear his or her own echo from the near-end location. The arrangement includes an echo suppression process which compensates for this effect by inserting loss in the transmit path of the speakerphone as appropriate. Operation of this process is such that whenever the speakerphone is in the receive state, the levels of a transmit and receive speech signal in the speakerphone are monitored. By monitoring these speech signal levels, the process determines when speech into a microphone in the speakerphone is being coupled from a loudspeaker also in the speakerphone and when the transmit speech signal level exceeds a predetermined threshold. If this threshold is exceeded, then loss that tracks an envelope of the receive speech signal is inserted in the transmit path.
December 28, 1988
Date of Patent:
December 18, 1990
AT&T Bell Laboratories
Richard H. Erving, William A. Ford, Robert R. Miller, II
Abstract: An adaptive nonlinear data driven echo canceller is disclosed. Unlike other approaches to nonlinear echo cancellation, the inventive echo canceller treats the nonlinearity of the echo path as nonlinear noise associated with transmitting data symbols through a linear echo path. In comparison to a conventional LMS data driven linear echo canceller, the inventive echo canceller utilizes only an additional small random access memory for storing a nonlinear function for estimating the effect of the nonlinear echo path on transmitted data symbols. The same LMS algorithm is used to estimate the linear echo path and the nonlinear function. The signal processing power of a conventional linear data driven LMS echo canceller is sufficient to implement the inventive nonlinear echo canceller and the convergence speed of the nonlinear echo canceller can be less than three times that of the conventional linear LMS echo canceller.
Abstract: A laptop device includes a personal computer, a cellular transceiver, a speakerphone, and a hybrid communications control unit. The device has connectors for attaching a headset, cellular control unit, land telephone line, and additional speakers and microphones. The microprocessor-controlled hybrid communications control unit includes a modem, a data access arrangement, and a tone generator as well as digital, analog, and power switches. The hybrid communications control unit switches the communications components and provides, under program control, the proper protocols, level, and impedance matching to connect the modem, speakerphone, headset, speaker/microphone, or cellular control unit to the landline or to the cellular network via the transceiver. Matching and switching operations are automatic and transparent to the user. The unit can also connect two of the terminal devices or connect the cellular and landlines for call relaying. The device is capable of connecting plural calls at the same time.
Abstract: An echo canceller includes a first transversal filter for generating a first echo canceling signal to be canceled from an output signal from a sampler, the first echo canceling signal corresponding to a first sampling value of an echo response waveform of an echo path by a sampling clock when no sampling clock jitter occurs, a second transversal filter for generating a second echo canceling signal corresponding to a difference between the first sampling value and a second sampling value when the sampling clock jitter occurs, two subtractors for canceling the first and second echo canceling signals from a digital reception signal output from the sampler, and a controller for detecting the sampling clock jitter and performing a control operation such that a tap coefficient value of the second filter is added to a tap coefficient value of the first filter to update the tap coefficient value of the first filter, and thereafter, the second echo canceling signal generating operation of the second filter is disabled
Abstract: A trunked communication system utilizes talkgroup synchronization for roaming communication units. By automatically matching the communication unit's talkgroup in a first area-wide system with an talkgroup in a second area-wide system, the communication system facilitates rapid association with a desired talkgroup.
Abstract: A loudspeaker apparatus is used for a radio telephone apparatus having a base unit and a radio telephone set. The base unit includes a loudspeaker for generating a speech signal from a wired telephone line coupled to the base unit. The loudspeaker is connected to the wired telephone line in response to a calling origination signal by an operation of calling origination key if the radio telephone set is installed in the base unit.
Abstract: An echo canceller of this invention cancels an echo signal input to a sampler through an echo path upon 2-wire/4-wire conversion. The echo canceller includes a filter having a characteristic for reducing a tail of an echo response waveform and inserted between an output terminal of the sampler and a reception output terminal, a first transversal filter for generating a first canceling signal for canceling an echo signal sampled at equal sampling clock intervals after the echo signal passes through the filter, a second transversal filter for canceling a deviation of a sampling value obtained when sampling clock is jittered before the deviation passes through the filter, an enable/disable unit for enabling/disabling a tap output of the second transversal filter, and a controller for, from a moment at which the sampling clock is jittered, controlling the enable/disable unit to cancel a deviation in correspondence with a deviation value of an actual sampling value.
Abstract: A radio telephone set comprises switch circuitry, a telephone circuit and a battery for portable operation, which battery may be a built-in battery. When the radio telephone set is not mounted on a vehicle, the switch circuitry is not connected to a battery of the vehicle and feeds power from the built-in battery to the telephone circuit. Thus, the radio telephone set can be used as a portable set. When the radio telephone set is mounted on the vehicle, the switch circuitry is connected to the vehicle battery and this connection causes the automatic switching of the power supply to the telephone circuit from the built-in battery to the vehicle battery. Thus, the radio telephone set can be used as a vehicle-mounted, or onboard, set.
Abstract: A shoulder rest used on a cellular-telephone handset has a forwardly directed mouthpiece, a forwardly directed earpiece spaced therefrom, and a relatively thick stem extending therebetween and itself having a back face provided with control buttons. The shoulder rest has a curved cradle shaped to fit over the shoulder of a user of the handset and a stem projecting upward from the cradle and having an upper end. A holder body fixable in a plurality of angularly offset positions to the upper end of the stem carries a pair of U-shaped clips spaced apart on the holder and each adapted to embrace a respective end of the handset across the back face thereof. Respective tightening elements are operable to close the clips on edges of the handset.
Abstract: A unique cellular telephone (100) connects to a standard telephone set (101) for providing cellular telephone services to subscribers in remote locations not served by a landline telephone system. Cellular telephone (100) includes a cellular telephone transceiver (109), microcomputer (108) and circuitry (102-106) for interfacing the cellular telephone transceiver (109) to the telephone set (101). The interface circuitry (102-107) provides the audio, voltage and dial signal interface to the telephone set (101). The microcomputer (108) controls the interface circuitry (102-106) and is responsive to the telephone set (101) for answering and placing cellular telephone calls. The microcomputer (108) also is responsive to dialing sequences including numerical digits preceded and followed by the # digit for selecting cellular telephone features.
May 10, 1989
Date of Patent:
September 25, 1990
Francis P. Tobolski, Jr., Robert F. D'Avello
Abstract: A radio telephone apparatus having a voice recognition function. A voice dial mode may be set for a predetermined time period in response to the actuation of a switch, whereby address data corresponding to an operator's utterances within a predetermined time period after the switch is actuated may be broadcast to a base station over a radio channel. The operator may confirm the address data to be broadcast by checking one or more indications which are visually or acoustically provided before the address data is broadcast.
Abstract: An acoustic calibration circuit in a voice switched adaptive speakerphone accurately determines the type of acoustic environment in which the speakerphone is employed. The calibration circuit measures the acoustics of the room by emitting a tone burst through a loudspeaker associated with the speakerphone and measuring the returned time-domain acoustic response with a microphone also associated with the speakerphone. Obtained from this response and processed by a computer in the speakerphone are the maximum amplitude of the returned signal, and the duration of the echoes. The amplitude of the returned signal determines what level of transmit speech will be required to break in on receive speech. The greater the acoustic return, the higher that threshold must be to protect against self-switching. And the duration of the echoes determine how quickly speech energy injected into the room will dissipate, which, in turn, controls how fast the speakerphone can switch from a receive to a transmit state.
December 28, 1988
Date of Patent:
September 25, 1990
AT&T Bell Laboratories
Richard H. Erving, Robert R. Miller, II
Abstract: A cordless telephone employed in a public telephone system provides mobility and service at reasonable cost to users of portable communications equipment. The system includes a plurality of base units which are accessible by a plurality of similarly configured cordless telephones. Each one of these base units is assigned and operates on one of multiple frequency channels and each one of the cordless telephones is capable of establishing a communications link with each one of these base units. Once a cordless telephone establishes communications with a base unit within its reception range, other cordless telephones within this reception range are precluded from establishing communications with this base unit or monitoring or otherwise interfering with communications between the cordless telephone and this base unit while the communications link is established therebetween.
Abstract: A flickering device for telephone sets includes a phone housing having all the necessary elements and telephone circuits disposed therein for effecting communication operations with an open section provided in one side of the phone housing, a transparent member installed in the open section of the phone housing, a flickering circuit electrically coupled with the telephone circuits having a plurality of light-emitting elements disposed therein in conjunction with the transparent member for effecting flickering illuminations thereat, and an external power supply connected to the flickering circuit for providing the required power therefrom. Whereby, flickering illuminations will be effected along with the incoming ringing signals and the voice levels of those communicating on the related telephone set during communications.
Abstract: The invention represents an automatic positive disconnect circuit for controlling the connection of a communication device having two signal conducting lines and sensing means for indicating the mode of said communication device. The circuit is designed to positively disconnect the first and second lines of the communication device when the latter is in the non-operating mode, to filter selected frequencies when in the operating mode, and to permit said communication device to otherwise operate in a normal manner whenever a call is received or a call is initiated.