Abstract: System and method utilizing the temporal separation and amplitude differences of signals for transmitting the signals in a bandwidth corresponding to one half of the frequency range present in the signals.
Abstract: A FDM/TDM transmultiplexer uses sampling rate multiplication to increase the sampling rate for time division multiplexed (TDM) to frequency division multiplexed (FDM) conversion and decrease the sampling rate for FDM to TDM conversion. The rate multiplication filters are realized digitally in order to exploit the computational advantage of Fast Fourier Transform (FFT) algorithm, and channel filtering is implemented by a single time-shared sixth-order elliptic digital recursive filter. A novel FFT processor and recursive filter are disclosed which may be used in the system.
November 7, 1977
Date of Patent:
April 22, 1980
Communications Satellite Corporation
George D. Dill, Atsushi Tomozawa, James R. Fillion, Mian Z. Ali, Clyde E. Burwell, Brady H. Warner, Jr., Richard W. Jones
Abstract: A circuit arrangement is described for the reception and transmission of switching data associated with communication signals being transmitted to or from an exchange in a telecommunication system. In the system the signals are transmitted between exchanges by pulse code modulation techniques. Each exchange is provided with separate receiving/transmitting devices for the communication signals and the switching data signals, and each communication receiver/transmitter has a switching data receiver/transmitter assigned thereto. The latter are connected to a common control unit.
Abstract: A remote gain controlled optocoupled device is disclosed utilizing a DC reference voltage in the output section to compensate for variations in the optocoupling characteristics of the circuit. The DC voltage level output of the photodetector, which is a function of the light transfer characteristics of the circuit, is compared to a remotely controlled reference DC level. The output AC signal level, which substantially tracks the DC voltage output, is gain adjusted under control of the compared DC voltage levels.
April 5, 1978
Date of Patent:
February 26, 1980
Bell Telephone Laboratories, Incorporated
Alexander Feiner, Chao Kai Liu, Sigurd G. Waaben
Abstract: An input signal containing information such as speech or music as well as near-stationary noise is applied in parallel to a noise-analysis circuit and a noise-reduction circuit, each of which comprises a plurality of bandpass filters covering the range of frequencies associated with the information. The absolute value, or a function thereof, of the output of each bandpass filter in the noise-analysis circuit is produced and smoothed. The presence of near-stationary noise in the input signal is determined by examining the nature of the smoothed signal in each band assuming noise has a frequency spectrum which does not vary with time or varies only within a narrow range over a predetermined period of time with respect to the spectral parameters of the information signal. If noise is detected, the noise-analysis circuit identifies spectral parameters of the information and/or noise in each band using the smoothed signal therein.
Abstract: An electronic reverberation apparatus, for producing artificial reverberation on a purely electronic basis with a digital computer, comprises a plurality of loops having different delay times and adapted to form sound repetitions of diminishing intensity. Some of the loops have short delay times and have an all-pass characteristic. Others of the loops have long delay times. The loops are provided with tappings each of which has a particular delay time associated with it. The delay times of the tappings themselves and the sums, differences and quotients of these delay times are in a non-harmonic relationship to one another. Each tapping feeds a corresponding damping element whereby the output from each successive tapping is reduced such that the reduction in energy corresponds to an exponential function, and a delayed and repeated combination of unreverberated input signals is fed to an output from the loop circuit. For naturalness the output of each reverberation delay unit is randomly damped.
Abstract: A synthetic-speech calculator includes a keyboard consisting of digit keys and function keys and one or more mode selectors, a desired number of registers for storing numerical information entered by the depression of selected ones of the digit keys, a read-only-memory for storing a large number of digital codes as sound quantizing information, counter means for specifying the address of the memory so as to take a specific digital code out of the memory, a digital-to-analog converter for converting the specific digital code taken out of the memory into an audible sound signal, and a loud speaker driven by the audible sound signal and producing an audible sound. The synthetic-speech calculator is adapted such that the audible sound signals are derived via the loud speaker by at least two different methods of sound generation. For example, when a voice start key is depressed, all digits of keyed information are produced in audible form with appropriate pauses.
Abstract: A voiced instruction identification system understands commands by examining a pattern of changes in short syllable (mora) sounds. Fundamental frequency is used as one symbolic value of mora for speech or humming sounds.
Abstract: A telephone set has a transmitter-receiver including a first portion for mounting a microphone, a second portion for mounting a speaker for loudspeaking, an earphone for low speaking with an opening formed in the first portion so that the side walls of the opening connect the microphone to the second portion without acoustic coupling between the first and second portions, and a base member shaped to support the transmitter-receiver. The base member has a telephone number operating board which is accessible through the opening in the first portion when the transmitter-receiver is positioned on the base member. A mechanical switch on the base member responds to the placement of the transmitter-receiver to effect switching between the loudspeaking and lowspeaking modes of operation. Also disclosed is a microphone support member which can support the microphone without exerting any adverse effect on the characteristics thereof.
Abstract: An improved expanding system is described for enhancing transmitted or recorded audio signals previously processed by anyone of several nonlinear amplifying techniques. The system is designed to divide the audio signal received into substantially discrete frequency bands and each band is separately expanded, independently of the other bands, so as to minimize "breathing" and "pumping".
Abstract: An emergency roadside telephone system includes a plurality of self-powered, emergency telephone terminals positioned at remote locations, such as along roadways, to permit communication with a central station in order to obtain emergency assistance. Each emergency telephone terminal has a transmitter and a receiver for communication with the central station, a handset for providing voice communication and a plurality of emergency switches carrying symbols representative of various types of emergency assistance required such that a caller can request emergency assistance either by voice communication with an operator at the central station or, if there is a language barrier, by actuating the emergency switches.
Abstract: A time division multiplex system includes pulse width modulation to provide an automobile interrogate and control system whereby either the driver or front seat passenger can manually-operate switches mounted on doors to control door locks, windows and seat positioners. The system includes a transmitter module located in the left front door which transmits information to receiver modules interconnected by a data line and located in the passenger doors and under the front seat. The receiver in the right front door is capable of modifying the information received from the transmitter and placing the modified data on the data line to permit control of the right seat adjuster and all of the vehicle doors from the control located in the right front door. Stall of window motors or door lock solenoids is avoided through priority logic.
Abstract: Apparatus for projecting movement of audio signals employs a plurality of variable-gain amplifier stages, the gain thereof being controlled by the states of an associated plurality of counters and decoders, to provide a spatial distribution of audio signals in such a manner that the signals are perceived as having a variety of geometric configurations, which configurations may be either dynamic or static. The apparatus is suitable for use with recorded or "live" audio signals. Various alternatives are also disclosed, including a sequencing circuit for allowing automatic variation of amplifier gain in response to various components of the audio signal itself. The apparatus may be configured for connection directly to power amplifiers, or for connection to recording devices.
Abstract: An improved telephone connector block construction permitting the convenience of blocks normally connected at parallel sidewalls thereof to be conveniently interconnected at a forwardly facing surface in those installations where side interconnection is not practical or desirable. The construction includes an element providing guiding means for jumper connections leading to the forwardly facing surface including the necessary fanning openings, and a second element forming pin terminal means on said forwardly facing surface. The improved structure permits the mounting of adjacent connector blocks at closer intervals than otherwise possible where specific installation sites require such closer spacing.
Abstract: The magnitude of current supplied to a subscriber telephone loop during both loop start and ground start modes of operation is controllably limited by employing a battery feed circuit including an adjustable line build-out impedance. Resistors are controllably switched in or out of the battery feed circuit leads as a function of the potential developed across the line build-out impedance in a predetermined one of the battery feed circuit leads. Since the line build-out impedance being adjusted in value is within the detection loop, there is hysteresis in the switch points for switching the resistors in and out of the battery feed circuit leads. This hysteresis minimizes possible oscillation at the switch points and, therefore, minimizes development of unwanted signals on the subscriber loop. The use of an adjustable line build-out impedance further allows use of small resistance value, low wattage resistors as line build-out impedance elements.
March 24, 1978
Date of Patent:
November 27, 1979
Bell Telephone Laboratories, Incorporated
Abstract: In the case where a two-wire circuit forming a trunk or a subscriber line of the two-wire system is converted by a hybrid circuit to a four-wire circuit of sending and receiving paths to form a transmission line between subscribers, if an impedance variation on the two-wire side is large, a leak from sending path to receiving path occurs and is amplified to cause singing. To eliminate the singing, a circuit for detecting the impedance fluctuation of the two-wire side is inserted in the two-wire circuit, and switching means inserted in the four-wire circuit is activated by an impedance detecting signal of the detecting circuit to electrically open the four-wire circuit, thereby preventing the singing phenomena. This method does not involve the use of an expensive attenuator which is troublesome to design for the prevention of singing.
Abstract: An intercom calling apparatus in a key telephone system including a page switch for switching the transmitter from a talking circuit network to an intercom calling path while a contemporaneous call on a central office line is held by the series combination of a resister and a varistor forming a parallel circuit with the transmitter in the talking circuit network.
Abstract: A ringing signal generator for generating a ringing current in a subscriber's line uses a line current inverter controlled by means of a pulse code modulated signal obtained by encoding a sinusoidal ringing signal by means of a delta modulator at a sampling frequency which considerably exceeds the frequency of the ringing current.
Abstract: This device enables apartment dwellers to communicate with and thereby identify persons desiring ingress to an apartment building through a controlled access vestibule. The convenience and security of a conventional intercom is provided by this device, but without substations and their associated dedicated wiring. Communication is initiated via residential telephones which effect a ringing signal (to be sent) from the central telephone office to the device. This device automatically answers the incoming call on the line, transmits an audible signal in the preferred embodiment, enables voice communication, and disconnects.