Abstract: In the illustrated embodiments, the signals to be transmitted are converted into electrical signals and are divided by means of filters into a plurality of frequency bands. The envelopes of the signals coming out of the filters are then employed for the modulation of tones. Finally, the original tones and the modulated tones are supplied to the hearing-impaired person as an audio signal. To this end, the disclosure provides that the original signal to be transmitted is transmitted together with the modulated tones, and that the ratio of the volumes of the original tones and those of the modulated tones is set to a ratio which is comfortable for the hearing-impaired person. The transmission of the modulated tones is at least partially interrupted for voiced sounds. Standard ear sets or implanted devices with direct electrical transmission of the signals to the auditory nerve can be employed for transmission to the hearing-impaired person.

Abstract: A high performance and extremely compact earphone is disclosed. The earphone includes a speaker unit and a case in which the speaker unit is mounted. The earphone is attachable to a cavity of a conha defined by the tragus and a confronting projection of the pinna of the ear. The earphone has a specific physical configuration such that the earphone is firmly fitted to the ear cavity by the resiliency and friction of the ear.

Abstract: An audio speaker system is disclosed providing improved fidelity of performance from overdamped woofer drivers in small sealed enclosures. At least two woofer drivers are employed, and are driven electrically in such a manner that the phase difference in the electrical signals to the two drivers, or sets of drivers if more than two are employed, will be near zero at the lowest bass frequency and will increase to a value up to 180 degrees at the highest bass frequency which is generally taken as the woofer-midrange crossover frequency. This aforementioned phase difference in the electrical signal inputs to two sets of woofers common to one sealed enclosure improves over prior art by providing increased low-bass acoustic output, less acoustic wave interference between the woofers and the midrange drivers, and a smoother input impedance characteristic in the bass frequency region.

Abstract: A voice response control system is disclosed which comprises a voice recognition unit adapted to recognize a voice instruction given thereto and operate a vehicle component in accordance with the given voice instruction. A control circuit is provided for turning down the sound volume of an audio set to a sufficient level to ensure correct voice instruction recognition before a voice instruction is given the voice recognition unit and returning the audio set to its initial condition at the termination of the voice instruction recognition.

Abstract: An automatic uninterrupted direct current power source switch utilizes a voltage controlled latching relay for switching over between direct current voltage sources, such as batteries, which supply power to a common load, with virtually no interruption in load current being experienced during the switchover. The power source switch is intended to be used with two independent direct current voltage sources in conjunction with a recording device which receives its power through either one or the other of the voltage sources, depending on the state of the latching relay. The latching relay will change state when the voltage powering the recording device reaches an adjustable trigger level which is below the nominal working voltage, provided that there is a second direct current voltage source connected to the power source switch and the second direct current voltage source has a terminal voltage near the nominal working voltage.

Abstract: A unidirectional dynamic microphone provided with a first sound path to the forward side of the diaphragm and a second sound path to the rear side of the diaphragm, a Helmholtz resonator disposed in the first sound path having a sound entrance, and a diffraction lens mounted ahead of the Helmholtz resonator and partially shadowing the sound entrance to the Helmholtz resonator for the purpose of increasing the high frequency response of the microphone.

Abstract: Improved apparatus for the linear predictive coding of human speech in which the speech is sampled through the use of analog filters and the linear predictive coding computations are performed with respect to such samples using digital techniques. The filters are MOS switched capacitor filters which can be implemented on a silicon chip together with the digital circuitry. Specific circuits for implementing two different linear predictive coding speech analysis techniques are disclosed.

Abstract: A piezoelectric cone-type speaker having a multiple structure in which a plurality of piezoelectric elements and speaker diaphragms individually coupled to them are coaxially or multi-axially arranged. It has a wide frequency range. A cushioning member is interposed between one diaphragm and another so that each element is isolated from the vibrations of another element.

Abstract: In this incoming audio detection circuit for a speaker telephone, an impedance element is connected between the output of the microphone amplifier and the telephone line terminals. Speech signals present at each end of the impedance element are respectively rectified but not filtered. The resultant rectified but unfiltered signals are compared. If only outgoing speech is present, the rectified signal derived from the microphone amplifier end of the impendance element will be of greater magnitude than, and will have a greater phase angle extent than the rectified signal derived from the telephone line end of the impedance element. A comparator senses this condition and maintains the speaker telephone in the outgoing audio mode. In the presence of incoming speech, instants will occur when the magnitude of the rectified signal derived from the telephone line exceeds that of the rectified signal derived from the microphone amplifier.

Abstract: Apparatus is disclosed for enabling a mobile radiotelephone to automatically attempt to seize a radio channel in a multichannel radio communication system. The mobile radiotelephone scans the radio channels for a non-busy radio channel and provides an indication signal when detecting a non-busy radio channel. A counter which is continuously clocked by a clock signal is incremented for each clock cycle interval of the clock signal in response to the presence of the indication signal and is decremented for each clock cycle interval of the clock signal in response to the absence of the indication signal. Thus, the totalized count of the counter is proportional to the degree of radio channel blocking of the radiotelephone system. After an unsuccessful channel seizure attempt by the mobile radiotelephone user, time interval generating circuitry provides a random time interval that has a maximum magnitude that is inversely proportional to the totallized count of the counter.

Abstract: A helmet having a built-in modulator and amplifier for voice alteration and projection is disclosed. The helmet includes a forwardly projecting nose housing having a viewing shield and an array of light emitting diodes. The light emitting diodes are coupled to the amplifier through a driver in which selected groups of the diodes are illuminated according to the intensity of the audio signal delivered by the amplifier. A loud speaker is mounted within the nose housing and is enclosed by a sidewall baffle. A microphone is mounted on the outside of the baffle and is connected to an audio alteration unit within the enclosure which includes an analog multiplier, a sine wave oscillator and an audio amplifier. The multiplier has an audio output corresponding to the product of the voice signal produced by the microphone and the sine wave oscillator signal. This produces a modulation effect which simulates an alien sound.

Abstract: A circuit which performs loop supervision, transmit, receive, and transmit and receive regulation and sidetone balance. A loading circuit shunts excess current from the transmit and receive circuits under short loop conditions. The loading circuit also controls regulation of the transmit and receive circuits. Use of constant current power supplies external to the transmit and receive circuits prevents modulation of the power supplies.

Abstract: A complete audio processing system of solid state design for providing improvement of audible signals through dynamic compression including an active filter for transient suppression, a gain control, and a plurality of active frequency control stages for selectively controlling internal gain of signals in different frequency bands. Outputs of the frequency control stages are mixed and provided to a compressor stage having an operational amplifier of gain fixed by a DC feedback network. A gain cell provides variable negative feedback. A rectifier circuit measures the average value of the audio input to the compressor stage and controls the gain cell as a function of the average value to provide negative feedback which increases as a function of increase in the level of said input signal. An attenuator receives the output of the operational amplifier and provides an attenuated but dynamically compressed output so that the circuit provides no substantial overall gain but achieves high compression.

Abstract: An audio signal processing system for producing a moving comb filter effect having an all pass phase filter or other suitable phase shifting device in a first input branch and a bypass circuit with an optional inverter in a second input branch. A frequency shifter is inserted either into the first or the second input branch. A first summing network is connected to the outputs of the first and second input branch. An optional second summing network is connected to the output of the first input branch and the inverted output of the second input branch. A feedback circuit may be connected between the output of one of the summing networks to the input of the system to enhance the moving comb filter effect. Also, at least one switching circuit may be used to obtain phase reversals in the frequency shifter thereby facilitating up or down detuning or successive up and down detunings of the comb filter frequencies.

Abstract: A speaker unit for headphones including a magnetic circuit which has a magnetic gap and including a diaphragm which is moveable to generate sound in response to energy applied to a coil wound on a bobbin which is connected to the diaphragm and mounted within the magnetic gap and including a frame for supporting the magnetic circuit and the diaphragm and a protecting means mounted at the front of the diaphragm and having projections so as to engage the diaphragm near the region where the bobbin is mounted so as to limit the maximum motion of the diaphragm and the protecting means formed with openings such that the protector prevents the bobbin from moving completely out of the magnetic gap. The invention is applicable to speaker units for open air type headphones, for example.

Abstract: The present invention is directed to a recording apparatus comprising feeding and receiving means for recording paper that are positioned under a recording surface and rollers, whereby either the feeding means and/or the receiving means can be removed from or installed through the top of the recording apparatus for changing the recording paper.

Abstract: A high resolution thermal print head and method of fabrication is provided in which resistive elements are located at the edge of a dielectric support which functions as a spacer and is sandwiched between opposing substrates which carry vertically running electrodes on their inner faces. The electrodes extend to the edge of the spacer where they make electrical contact with opposing sides of the resistive elements. In one embodiment, the resistive elements are recessed into the edge of the spacer to minimize wear. The edge-on contact provided by the print head with the printing paper provides that all the supporting circuitry is orthogonal to the plane of the paper. In one embodiment, the spacer is provided with channels for coolant which is circulated immediately beneath the resistive elements.

Abstract: Three microphone units of first order sound pressure gradient unidirectional type are disposed in a casing having front and rear portions at both sides in such a manner that the center axes of the microphone units are aligned on the same axis. Two among the three microphone units are arranged to face the front portion of the casing, and remaining one microphone unit is arranged to face the rear portion of the casing. The output signals of the three microphone units are combined at a variable ratio so that the directivity of the microphone system can widely vary from nondirectivity via first order sound pressure gradient unidirectivity to second order sound pressure gradient unidirectivity. The output signals of two microphone units used for obtaining second order sound pressure gradient unidirectivity may be respectively applied to high pass filters before being combined, and the combined signal is fed to an equalizer.

Abstract: A modular wiring system is disclosed for lighting and power distribution in office buildings, factories and the like. The modular wiring system utilizes a five-face connector assembly as its principal component for the distribution and control of power to lighting fixtures and power receptacles. The connector assemblies may be one of four types for providing different power configurations at the connector faces. The five-face connector assemblies all utilize the same housing and are economical to manufacture by using specially designed bus bars to obtain the desired power configurations and to provide the terminal connections. Other components of the wiring system mate with the five-face connector assembly to provide an efficient lighting or convenience power system which may be easily field modified.

Abstract: A communications system, in particular a telephone system, is provided for the connection of mobile subscriber terminal devices via radio links, in which a central and/or sub-central location there are arranged storage devices which, for all of the users, each store an item of information concerning the relevant location of a user. The particular stored item of location information is used to control the switch-through of a connection to be established to the mobile user. The subscriber terminal devices include identification read-out devices for reading user identification cards. The subscriber terminal device temporarily receives the user call code stored on the user identification card which provides the facility of passive access to the user. Facilities are also provided for automatic charge accounting.