Abstract: A system for signalling the fact that the fuses and limiting diodes in the connecting circuits of telephone lines are defective. Use is made of the rest supply resistors already present in the connecting circuits and the loop detector which is normally used for detecting calls. The fuses and limiting diodes are connected in such a way that a defect causes the loop detector, which is constructed as a differential voltage detector, to signal a call.

Abstract: A telephone card index, having a switch connected to the card finder for initially locking on to a memory section of a miniprocessor, a key aligned with each name line of the card locates the exact memory address of the number to be called with pre-recorded dial signals at the memory address for an individual name line, permits automatic telephone dialing of the selected number. A keyboard in the circuit, with a display permits adding, changing or recalling the recorded number at each address.

Abstract: A pitch and voiced/unvoiced detector comprising a low pass filter or variable cutoff frequency low pass filter for providing a constant power output, DC shifting and weighting circuits operating on the filtered analog signals, a summing circuit for the filtered and weighted signals, a peak detector with controlled exponential decay time and timing circuits which are used to distinguish pitch and voiced/unvoiced structure in the analog input signal.

Abstract: A base plate for a telephone set is molded of plastic instead of being a metal stamping and can be made of recycled scrap plastic material. The base plate is provided with a plurality of positions for mounting telephone set parts with each position having an arrangement of projections and one or more deflectable members whereby the telephone items can be mounted by sliding and downward movement to clip in, and with one or more of the positions also having alternative means for mounting items whereby alternate forms of an item can be interchangeably mounted.

Abstract: A six-telephone channel conference system features an all-digital CVSD (continuously variable slope delta modulation) conference bridge-like circuit. The delta modulation pulse train in each channel is transformed into a series of slope numbers which are processed by the conference circuit addition function to provide zero insertion loss, then by the subtraction function to provide 100% cancellation of a talker's voice to his ear. Transformation involves a sequential three-bit algorithm.

Abstract: A hybrid bridge circuit has a feed amplifier and an auxiliary resistor connected in series with the output of the receive amplifier between the amplifier and a node of the bridge so that signals from the receive amplifier are transmitted through the two-wire line port in the bridge to the auxiliary resistor and a resistive leg of the bridge, and signals from the two-wire line are transmitted to both the node V1 between the two-wire line port and the adjacent resistive leg of the bridge and the node V2 between the compensating network in the bridge and the adjacent resistive leg of the bridge. A differential transmit amplifier differentially receives inputs from the nodes V1 and V2 so that the differential amplifier produces a partially equalized output signal corresponding to the difference between the voltages at the nodes V1 and V2. The resistance values R1 and R2 of the two resistors legs of the bridge, and the impedances Z.sub.c and Z.sub.

Abstract: A telephone handset is formed from two elongate hollow concave parts, joined at their peripheries, with a circular recess at one end of the lower part. A transmitter assembly is positioned in the recess and comprises a transmitter, a cup-shaped member positioned on the back of the transmitter and a resilient tubular member surrounding the transmitter and at least the lower or front part of the cup-shaped member. The tubular member has a radially inward projecting rim at its front or lower end extending over the front of the transmitter and a similar rim at its rear end engaging over a projection on the cup-shaped member. The resilient tubular member retains the transmitter and cup-shaped member together, and acoustically seals them together and also acoustically seals the front of the transmitter to the base of the recess.

Abstract: The following specification discloses and teaches a solid state ringer or audible alarm for a telephone. The ringer can be connected to the tip and the ring sides (i.e., plus and minus terminals) of a telephone network in the home, or any other location. The ringer incorporates a rectifying bridge and a two terminal current regulator for providing current to the network on a regulated basis to eliminate undue irregularities on the line. The ringer can be rung on a duty cycle similar to a mechanical bell by means of charging a capacitor that discharges in accordance with the duty cycle of the mechanical ringer. The cycle is established through a timing network formed with a resistor within the timing loop incorporating the capacitor. The capacitor is discharged to power a speaker through a switching network by means of three transistors that provide a switching function. The discharge provides a voltage across an oscillatory network that allows a unijunction transistor to operate a speaker.

Abstract: In a mobile telephone system of the type in which the service area of the system is divided into a plurality of radio zones, mobile-system base stations are installed in respective radio zones, each mobile-system base station is connected to a mobile-system control unit through a common control channel and a plurality of speech channels, and the mobile-system control unit is connected to an existing telephone network via a mobile-system exchange unit, there are provided signal lines extending between the mobile-system base stations and the mobile-system control unit and between the mobile-system control unit and the mobile-system exchange unit and respectively combined with each of the speech channels. These signal lines are used to determine the state of the speech channels, and to transmit control and information signals.

Abstract: The speech synthesizer minimizes storage requirements by storing basis functions each defining a waveform segment or phoneme within a pitch period and including formants F1 and F2, featuring readin at one rate and readout at different rates within the pitch period. The synthesizer is characterized by each basis function being represented by a data point plotted on a single line on a chart having first and second formant log-log axes and means for producing a speech waveform segment approximately representing any desired point located off of the single line on the chart by selecting and reading out of the memory one of the basis functions at a rate different than the basic storage rate.

Abstract: A flexible acoustic coupler includes a pair of muffs and at least one acoustic-electrical transducer located in one of the muffs. Each of the muffs is arranged to support either the mouthpiece or earpiece of a conventional telephone handset. The muffs, in turn, are joined by a flexible coupling element which normally supports the muffs spaced apart so as to be mated in acoustic coupling relation with a conventional telephone handset. The flexible coupling element, however, is capable of flexing so that one muff can be rotated 180.degree. with respect to the other muff and mated therewith to thereby reduce the space taken up by the coupler when not operating. In implementation, the flexible coupling element and both muffs are integrally molded providing an attractive and efficient low cost acoustic coupler.

Abstract: Digital echo canceler for a modem for data transmission by means of phase and, possibly, also amplitude modulation of a carrier, the ratio between carrier frequency f.sub.o and modulation rate 1/T having the form P/Q, P and Q being integers.The echo canceler receives the binary data to be transmitted for generating an echo copy signal. An echo canceler of a simple implementation is obtained in that the echo canceler comprises means responsive to each symbol configuration at each instant iT for generating at least a number depending on the amplitude allotted to the carrier at said instant iT and for applying this number to at least a given section of an assembly of adaptive digital filter whose output signals are combined for forming a digital version of the echo copy signal, the coefficients of these filters being adjusted by an assembly of adjusting circuits receiving said error signal in digital form and arranged for minimizing a predetermined function of said error signal.

Abstract: A device for electronically simulating vibrato, chorus, and pseudostereo effects and the radiation effects produced by a rotary loudspeaker with the aid of two loudspeakers or loudspeaker combinations, in which device a controllable amplifier is associated with each loudspeaker, the audio signal being applied to these amplifiers both directly and via a delay means, and both the delay and the gain of the amplifiers being varied synchronously by a subaudio-frequency generator.

Abstract: A telephone amplifier and attenuator circuit comprising an amplifier and an attenuator inserted in the transmit channel and an attenuator inserted in the receive channel of a telephone set. The speech signals conveyed by the transmit and receive channels are detected and added together for forming a sum control signal. The transmit amplifier is controlled by the detected transmit signal and the two attenuators are controlled in opposite directions by the sum control signal. In the preferred embodiment, the amplifier and attenuators are formed respectively by a balanced modulator and by balanced modulators inserted in the loop of negative feed back amplifiers.

Abstract: A method of determining the fundamental frequency or pitch period of a voice signal from a difference signal, formed with the aid of predictors, between the original voice signal and the voice signal estimated by the predictor. Only the significant characteristics of the difference signal are then auto-correlated and the maxima of the correlation coefficients determine the fundamental frequency or pitch period.

Abstract: A system is described for randomly addressing any one of a plurality of remotely located stations connected by means of an electromagnetic wavepath. At the addressing point an addressing signal, comprising a series of m signal bursts, is generated and coupled onto the wavepath (11), where m is an integer and corresponds to the number of stations the addressed station is away from the addressing point. Each remote station includes means (33, 34, 41, 43) for deleting one signal burst and retransmitting the remaining signal bursts. Each station also includes means (34, 38, 42, 43, 44, 50, 51) for recognizing when only a single signal burst is received and for responding in a prescribed manner. By means of such a "count-down" technique, the m.sup.th station from the addressing station is accessed. it is an advantage of such a system that the addressing circuit is the same at all the remote stations.

Abstract: An address verification system is described for use in a communications system comprising a transmission path (14) having sequence of remote stations (1, 2, ... n) distributed therealong. After accessing the desired station, a loop-back (32) is established at the addressed station to a second transmission path (15) having a second sequence of stations (1', 2' ... n'). Verification is obtained by transmitting a series of p+1 signal bursts, where p is the total number of stations in the loop-back path. By designing each station so that it deletes one of the signal bursts, a single burst will be received at a verification detector (23) when and if the proper station is addressed. It is an advantage of the invention that it can be used with all types of communication systems. It is a further advantage that it permits the use of identical repeaters at all the remote stations.

Abstract: A method and apparatus is provided wherein the total elapsed time for a series of outgoing calls on a plurality of call lines of a telephone is accumulated for each of those lines by a plurality of clocks and switches operating in a monitoring circuit for the output lines. An operator of the telephone may note the accumulated time on each line so as not to exceed an allotted time as is used in different regions of wide area telephone services (WATS). When the timing apparatus is used with a key telephone, the timers are controlled by individual reed switches, each of which is associated with a respective key switch and activated by a magnet attached to said key switch.

Abstract: A telephone transmission system has repeaters spaced along both the transmit and receive legs of the transmission line, with a power supply for the repeaters including a current regulator having positive and negative supply lines connecting the power supply to the two legs of the transmission line. Current surge protectors are connected from the two legs of the transmission line to ground. A pair of current sensors responsive to the current levels in the positive and negative supply lines, between the power supply and the current surge protectors closest to the power supply, produce output signals representative of the respective current levels. A control signal generating means receives the output signals from the current sensors and produces a control signal in response to a deviation of the higher current in the supply lines from a preselected reference level. The control signal is supplied to the current regulator to maintain the higher current level in the supply lines at the preselected reference level.

Abstract: An accessory attaches to the outside of a dial telephone, fits around the dial, and has a main switch actuated by movement of the handset of the telephone. The accessory includes a rotatable element arranged to encircle the dial and a dialing switch responsive to rotation of the element and the dial to produce pulses as a number is dialed. Electronic logic circuitry processes the pulses from the dialing switch and operates displays for displaying a dialed number digit-by-digit and for spacing the dialed digits into groups conforming to telephone number digit groupings for local calls, long distance calls within the calling area, and long distance calls outside of the calling area. The accessory also preferably provides dashes between groups of displayed digits and includes a timer for automatically measuring and displaying the elapsed time of a call.