Abstract: Speaker mounting apparatus for front mounting a speaker to a panel of an automobile or recreational vehicle, including a base containing an opening for the speaker cone support and a peripheral flange containing recesses into which are snapped the tabs of a retainer ring which holds a speaker cover which decoratively covers the speaker and the mounting hardware. The base can be independently mounted to the panel and the speaker mounted to mounting posts. Alernatively, single screws can be used to simultaneously attach both the speaker and the housing to the panel.

Abstract: This speaker recognition system offers improved recognition by comparing the mean and variance of an unknown (test) speaker's Orthogonal Parameter signals versus those of previously-stored known (reference) speakers. The unknown speaker's Orthogonal Parameters represent his hypothesized identity because his original speech linear prediction coefficients are transformed into his set of Orthogonal Parameters using the stored (reference) transformation coefficients of each of the previously-recorded known speakers.

Abstract: A ringer isolator is used in conjunction with a pair of telephone lines to isolate ringer coils coupled to one of the telephone lines from a reference terminal except when a ringer signal is applied to the telephone lines. The ringer isolator includes an isolator such as a neon lamp/photo resistor coupler or a transformer partly coupled between the telephone lines and partly coupled to a thyristor such as a silicon controlled rectifier or a triac. The thyristor is coupled in series relationship between the ringer coils and the reference terminal. Normally, the thyristor is maintained nonconductive so that the ringer coils cannot be energized by potentials on the telephone lines. In response to the ringer signal being applied to the telephone lines, the isolator enables the thyristor to be rendered conductive so that the ringer coils are energized by the ringer signal.

Abstract: An echo suppressor for use in the send path of the four-wire part of a long distance telephone circuit employs frequency-selective center clipping. The bandwidth of the channel in which echo occurs is subdivided in contiguous bands or subchannels by appropriate filtering, and each resulting signal is center clipped by a center clipper. Threshold control voltages are predicted from knowledge of the average speech amplitude distribution characteristic as a function of frequency. This characteristic is subdivided into the same frequency bands as that used by the center clippers, and the ratios of energies in the bands are used to equalize the ratios of the control voltages that determine the center clipper thresholds. This technique is implemented through the use of a peak rectifier, the input of which is coupled to the receive path of the echo suppressor and the output of which is connected to each of the filtered subchannels by a resistive dividing network.

Abstract: Universal/Assigned Night Answering system incorporated in an EPABX system permits any telephone station to answer a universal incoming call or an associated assigned incoming call from incoming trunk line while retaining the ability to initiate calls to other telephone stations within the EPABX system or to outgoing trunk lines. A UNA/ANA module is provided using a standard half-register for UNA operation and circuitry for ANA, the module also being coupled to the common control line and having its own vertical line in the switching matrix.

Abstract: A molded rubber tubular member includes a grommet-like flange at its open end for permitting the structure to be attached to a panel. A recessed nest portion is provided at the opposite end of the tubular member into which is inserted a transducer whose diaphragm serves as a closure at the end of the tubular member. The assembly serves as a flexible shock mount for the transducer and also as an acoustic amplifier which increases the acoustic sensitivity of the transducer by 10 to 20 dB in a selective frequency band within the audible range.

Abstract: A multiple frequency signalling receiver translates combinations of tone signals received from a telephone set to derive binary two out of eight coded signalling. Received signals are directed by a filter to high and low band translator circuits. Each translator circuit includes a circuit for deriving a threshold signal from the received signal and a threshold signal controlled limiter for limiting the received signal. The threshold signals are cross coupled between the limiter in each translator to prevent response to signals in the high and low bands being substantially unbalanced in amplitude. Digital counting and decoding circuits in each translator circuit detect predetermined frequencies of signals from the limiting circuits. Upon occurrence of a consistent detection by both the translator circuits lasting for at least about 40 milliseconds, the appropriate two out of eight code is gated to the output terminals of the multifrequency receiver.

Abstract: A transducer switching system for, in effect, removing electrical energy from a transducer without breaking the electrical circuit. A resistor is in series with the transducer. An electro-mechanical switch shunts the resistor. The switch is within the enclosure containing the transducer. When the acoustic connector of a use-element, such as a stethoscope type headset for a listener, is inserted into the enclosure the switch is changed from its normally open state to a closed state, thereby shorting out the resistor and allowing an effective level of electrical power to operate the transducer. Two systems may be simultaneously actuated for stereophonic sound.

Abstract: A maximum value tracing circuit employed in echo suppressors and the like for selecting the peak values of digitized voice signals. The digitized value of a signal previously stored in a register is continuously compared with the present digitized value. The larger value of the compared signals is stored in the register after application of each clear signal to the register.First and second maximum value tracing circuits of the type described may be employed in combination with a comparator-selector circuit for comparing the outputs of the first and second maximum value extraction circuits to produce a comparison output signal representative of the larger of the two compared outputs derived from the first and second maximum value extraction circuits, which output signal is utiized for providing reliable, high speed echo suppression.

Abstract: A headphone comprising: two ear cups; a head band; and coupling means for rotatably coupling the ear cups to the head band, the ear cups having ear pads on those sides facing each other, respectively, the head band being positioned on that side of each of the ear cups away from the side where the ear pad is provided, said coupling means rotatably coupling the head band to that side of each of the ear cups located away from the side where the ear pad is provided, whereby the coupling means enables each of the ear cups to make vertical and horizontal rotations relative to the ear of the user. This headphone insures free rotation of the ear cups in universal directions, and the rotation angle can be controlled as required. Moreover, the headphone as a whole can be provided in a compact size.

Abstract: A body of foam substance forming a head-rest, for example a head restraint for an automobile seat, an aircraft seat, or the like, provides a housing and support for the loudspeaker; the forward or head-supporting surface has at least one recess, open to the front, formed therein in which the loudspeaker is located and supported. The portion of the foam material in the recess behind the loudspeaker has open pores whereas the outer or remaining surfaces of the body are essentially airtight, for example by having their pores closed or by being covered with an essentially airtight upholstering material, perforated only in the region through which the sound from the loudspeaker is to be transmitted. This arrangement permits flexible or soft membrane suspension of the loudspeaker and thus better transducing fidelity.

Abstract: Echo propagation is prevented on four-wire signaling path to two-wire signaling path connections. A first transmission path portion is extended from the receive leg of the four-wire signaling path to the transmit leg and a second transmission path portion is extended from this point to the two-wire signaling path, the first and second transmission path portions thereby forming a bidirectional path carrying signals from the two-wire signaling path and from the receive leg. Detection circuitry is located in the first transmission path portion and develops a voltage signal which determines the direction of signal transmission between the four-wire and two-wire signaling paths. Echo propagation is prevented during signal transmission from the four-wire signaling path to the two-wire signaling path by opening the transmit leg of the four-wire signaling path.

Abstract: A headphone supported at the ear position for reproducing sound comprises (a) an oscillating member for sound reproduction, (b) a frame to support the oscillating member, (c) at least one opening constituting a path from the space, defined by the inside of the oscillating member, an ear pad and the ear to the free space on the outside of the oscillating member, and (d) an acoustic resistance member disposed in the opening.

Abstract: A headphone supported at the ear position for reproducing sound comprising (a) a frame, (b) a cone membrane, (c) at least one opening provided in the frame to connect the space, defined between the front face of the frame and the rear face of the cone membrane, and the free space at the rear part of the frame, (d) a member for applying acoustic resistance to sound which passes through the openings, and (e) a mask member to vary bass reproduction characteristics by varying the area of the opening providing the acoustic resistance.

Abstract: A single channel carrier system is disclosed including a remote terminal having a battery charger for charging a battery during idle periods to power the remote carrier electronics. The remote electronics include a ringing generator and a supervisory circuit to implement normal telephone supervision over the carrier channel.The ringing generator is a dc-to-dc converter for stepping the battery voltage up to the ringing voltage level. In order to interrupt this unipolar ringing voltage and thereby to energize the telephone ringer, a switching circuit is provided including a transistor in shunt with the ringing voltage supply to provide a return path for alternate half cycles of ringing current. A constant current source from a low voltage supply connected to the base of the transistor provides bias current to saturate the transistor yet minimizes the amount of dissipated power.

Abstract: Signal transmission circuit characteristics are supplemented by a negative conductance circuit in which current sources of complementary polarity are connected in shunt between the conductors of the signal circuit. Changes in the voltage level of one side of the signal circuit are sensed at a point common to the two sources and applied through a positive impedance to control the current output magnitude of one of the sources for effecting a supplementing of the signal circuit current as though the changed voltage level had been applied in the presence of a negative form of that impedance connected at that common point.In additional embodiments, different, or variable, positive impedance are connected in the sensing circuit output coupling to cause the negative of such impedance to appear at such signal circuit terminal.

Abstract: An improved headband is described for use in the clinical evaluation of hearing and hearing problems. There are a number of important tests of hearing which utilize test probes and other ear testing members which are conveniently held in place at the patient's ears using headbands. The headband described herein has improved means for adjustably positioning the probes or other test members and particularly for both aligning the probe and for adjusting the probe tip seating or sealing pressure at the ear canal under test. A universally adjustable probe mounting is provided on the headband for adjusting the attitude of the test probe tip and the probe support includes means for adjusting the force urging the probe tip into the ear canal under test.

Abstract: By identifying and analyzing the properties of the parameters of an input signal that contains speech in the presence of simultaneously occuring near-stationary noise, pauses between speech intervals as well as the termination of such noise can be recognized. When a pause interval containing noise is recognized, the parameters identified during such interval are used to set the parameters of an adaptive filter through which the input signal is passed during subsequent intervals of speech and until the noise terminates. During the time the input signal passes through the filter, the near-stationary noise is filtered out. In response to recognition of the termination of noise, the input signal is caused to by-pass the filter which is then prepared to accept the parameters of noise occuring in a subsequent pause.

Abstract: Centering device for an adjustable transverse filter of a digital echo canceller in a telephone network, in which said transverse filter produces samples of a synthetic echo signal y (t) deduced from N servo-controlled weights C representing the samples of the pulse-response of the echo path and deduced from the same number of samples X (T) of a signal x (t) in the reception line, and in which the N samples X (T) are delayed in a delay circuit ahead of said transverse filter, the delay time being given by the minor rank of said coefficients C lying above a threshold value, this minor rank being detected at the end of given convergence time of said transverse filter.

Abstract: A conference port for permitting simultaneous voice communication among a plurality of local stations and an external or central office line is shown. The stations may be part of a time division PBX or may be arranged as a time-sampled key telephone system having access to the same line. The conference port includes a first operational amplifier for summing the station port voltages on a capacitor during an interval that is a predetermined fraction of the resonant transfer interval. This first, or quasi-resonant, interval is sufficient to reduce the initial voltage on each of the station port sampling capacitors to a predetermined fraction of their initial level. At the conclusion of this interval the voltage on the summing capacitor in the conference port is multiplied by an appropriate factor in a second operational amplifier and is applied back simultaneously to all of the conference ports together with the signal incoming over the external or central office line.