Abstract: In a system of transceivers which can automatically operate either in calling or called modes, the identification codes of the calling and called transceivers are transmitted back and forth between them and compared in a manner which tends to minimize erroneous connections and to confirm only correct connections prior to starting the actual transmission of data between the transceivers.

Abstract: An improved loudspeaker system comprises an active crossover network for dividing the signal energy of an input audio signal into at least first and second frequency ranges separated by at least one frequency band, and at least a third frequency range including at least a part of the frequency band. The number of power amplifiers normally associated with a typical, similar powered loudspeaker system is reduced by combining the signal energy of the audio signal with at least the first and second frequency ranges so as to produce a first component signal and utilizing the signal energy in the third frequency range to form at least, in part, a second component signal.

Abstract: A frogging signal repeater for a transmission line communications system such as a telephone system having a trunk line connected between a pair of signal sources such as end central offices and/or standard signal repeaters. Each signal source generates information signals on a group of relatively high frequency carrier signals and receives information signals on a group of relatively low frequency carrier signals with the frogging signal repeater connected in the trunk line for translating the high and low frequency groups.

Abstract: A fluxbucking line transformer is disclosed in which fluxbucking primary windings in the line transformer compensate for the DC flux generated by the passing of DC currents by the primary windings. No feed-back circuitry is required for sensing the DC components of the magnetic field in the transformer core or to sense the DC current through the transformer to provide adjustment of the fluxbucking current. The disclosed transformer circuit is a bridge configuration which cancels the DC flux independently in separate primary windings, and is advantageously employed in telephone line circuits in which large DC currents are passed through the line transformer while smaller ac signals are coupled to the secondary without distortion of the ac signals due to saturation of the transformer core.

Abstract: Operating power for line signal repeaters is fed over a transmission cable pair (signal line) which is susceptible to lightning strikes and, thus, to longitudinally induced currents in the DC power feed circuit. A symmetrical non-linear power regulator is connected between the signal line and the line signal repeater, and includes a high current shunt regulator which bypasses excessive induced currents. By so doing the adverse effects of these induced currents on the operation of the line signal repeater is minimized. A shunt voltage regulator provides the line repeater with a constant operating voltage when the line current (DC line power feed current plus induced currents) is greater than the minimum required bias current. When the potential at input terminals of the power regulator exceeds a predetermined value, a portion of the excess current is conducted through a blocking diode to charge an energy storage device.

Abstract: A connector arrangement for optical fibers which includes programmable means for presetting an equalizer in a repeater connected to the fiber or adjusting the laser or LED power levels in a transmitter connected to the fiber. The equalizer coefficients (or the output power) depend on the fiber characteristics which remain constant at all times. Therefore, it is possible to preset the coefficents (or power) when replacing a repeater or a transmitter.

Abstract: A magnetically operated switch especially useful in telephone applications includes a transformer having a plurality of windings on an E-frame core and a reed switch magnetically coupled to the core by a plurality of high permeability strips which are placed in juxtaposition with the core and which have rolled end portions for supportably receiving the reed switch. The switch may be used in a hybrid junction for dial pulse detection.

Abstract: A small dimension low frequency loudspeaker has a folded exponential horn which provides a unitary curved sound path from an electroacoustic transducer at the throat of the horn to a volume into which sound is radiated at the mouth of the horn. The length of the horn is such that, at an exponential rate of expansion between the throat and the mouth, the mouth, when it is bounded by at least one planar surface, such as a floor, a ceiling, and/or walls of a room, has adequate area to enable reproduction of low audible frequencies. An illustrative embodiment of the low frequency loudspeaker has an effective low end cut-off frequency of 55 Hz. A loudspeaker system, including a low frequency loudspeaker as well as midrange and high frequency loudspeakers and an LC crossover network, is also disclosed.

Abstract: A portable self-contained amplified and loud speaker system and apparatus is disclosed herein having improved acoustical energy propagation in connection with musical sound distribution by a musician in a marching band or group. The apparatus includes cylindrical housing provided with shoulder and waist straps and a removable back plate shaped to fit the small of the back of the person wearing the housing. An electronic component package is secured within the housing so that a control panel is exposed for volume adjustment, recording tape insertion, start/stop switches and the like. Loudspeakers are angularly fixed to the opposite ends of the housing so as to close the ends thereof and are operably coupled to the components carried in the package for radiating acoustical energy in response to amplification of electrical signals processed by the components in a predetermined propagation pattern.

Abstract: An electro-acoustic terminal unit for use in an audio teleconferencing system comprises a loudspeaker and one or more microphones each having a sensitivity which is directionally dependent and exhibits at least one null or substantially null position. The loudspeaker and microphones are rigidly mounted on a boom and the microphones are so located and orientated relative to the loudspeaker that the null position is directed towards the loudspeaker.

Abstract: Acoustic intensity is measured by a pair of closely spaced microphones aligned in a given direction. One microphone is connected directly to an integrator the output of which is connected to a multiplier while the other microphone is connected directly to the multiplier. The multiplier output is proportional to the imaginary part of the cross-spectrum of the two microphone signals which when time averaged represents the absolute value of the sound intensity in the given direction if the microphone systems are properly phased matched.

Abstract: A line voltage sensor and dial pulse repeater circuit for use in conjunction with a digital PABX telephone system connecting a subscriber station to a switching center providing for detection of off-hook condition of the subscriber's set, detection of irregularly shaped dial pulse and correction of the irregularly shaped dial pulses to allow accurate reconstruction of the dial pulses originally transmitted via the subscriber's set.

Abstract: A bilateral transmission line repeater is disclosed in which opposite directions of transmission are separated into different frequency bands. The amplifiers for each direction of transmission include an automatic gain control circuit for controlling the gain of the amplifier. Gain control for the inward bound amplifier (toward a central location such as a telephone central office) is under the control of an automatic gain control signal derived from the outward bound signal as well as from the inward bound signal. Feedback around the gain control amplifier is accomplished using a current mirror circuit to avoid loading the amplifier output.

Abstract: A telephone set adapted to provide the calling person with a convenient grip of the hand set. The seat accommodating the handle is shaped as a channel whose sides surround the handle along its middle part so that the person making the telephone call cannot seize this part but, instead, will seize the lower (microphone) part.

Abstract: A gain and frequency compensated barrier circuit is disclosed for use with a telephone transmission line having variable loop lengths. A DC component of the input signal is provided to the input side of the barrier circuit. Loop length losses, as well as barrier gain variations, are adjusted on the output side of the circuit by comparing a barrier DC voltage level with a DC reference level and adjusting the AC gain in accordance therewith. Frequency response, which is also a function of loop length, is corrected by using the DC input voltage to generate an effective loop length dependent capacitor for further controlling the output signal level. An optocoupled circuit is disclosed for use in one embodiment of the disclosure.

Abstract: An audio signal transmission circuit comprising a first variable attenuator (i.e. volume controller) from which a level-adjusted audio signal is derived, a tone control circuit connected to the output of the first variable attenuator and supplying a tone-controlled audio signal to a loudspeaker, and a second variable attenuator connected between the tone control circuit and a record terminal and feeding the tone-controlled audio signal to the record terminal. The first and second variable attenuators are mechanically interlocked and arranged in such a way that the sum of their attenuating factors remains constant irrespective of any attenuating operation. At the record terminal there can be obtained the tone-controlled audio output signal with a substantially constant level (amplitude level), irrespective of the level adjusting operation of the signal to the loudspeaker.

Abstract: Constant-percent break pulse correctors ensure that the break interval of a dial pulse signal subsists for a substantially constant percentage of the total dial pulse interval, i.e., break interval plus make interval. The pulse corrector also delays via an operate timer and a release timer initiation of pulse correction cycles and other supervisory functions. Erroneous generation of corrected output dial pulses is effectively eliminated by completely isolating the release timer from the pulse corrector and by controlling the operate timer to generate a single narrow output pulse for initiating only one pulse correction cycle during each valid operate interval. The pulse corrector employs a control arrangement in conjunction with a counter to initiate a pulse correction cycle upon detection of a valid operate interval.

Abstract: Pulse signals, for example, dial pulses, wink signals or the like, have been corrected to have minimum break and make intervals by employing at least two analog resistor/capacitor type timers, usually connected in tandem. These prior timer arrangements are not readily implemented by employing large-scale integration because of their use of analog circuit components. Indeed, it is desirable to correct pulse signals to have at least minimum break and make intervals (FIG. 2) by employing digital techniques. To this end, a control signal (ENO) for determining the minimum break and make intervals is generated by utilizing a single digital counter (35) and associated logic for controllably supplying first (Y15) and second (Y30) timing signals (from 34) to the counter (36). The frequencies of the first and the second timing signals are selected in relationship to the desired minimum break and make intervals, respectively.

Abstract: The housing of the telephone subset consists of one piece made of a plastic material preferably shaped by a blow-moulding technique. The housing has a frontal sloping opening which is covered by a detachable control panel to which all the usual built-in components of a telephone subset are mounted.

Abstract: Improved circuitry for providing bass control in audio playback systems using feedback circuits wherein undesirable deviations in frequency response above the bass region exhibited by previously available Baxandall feedback circuits are substantially eliminated by utilizing, in a preferred embodiment, a voltage follower amplifier, such as an emitter-follower transistor circuit in association with a single capacitance in the bass control circuit, which eliminates the undesirable frequency response deviations at the mid-frequency and higher frequency ranges so that frequency response curves at all settings of the bass control substantially coincide above the bass region.