Abstract: In order to couple an input end of an optical fiber to a light source designed to illuminate same with message signals, the light source--such as an LED--is mounted on a dielectric disk where it is surrounded by a flat ring confronting another ring with a stepped inner profile from which a cylindrical sleeve projects on the side opposite that disk. A capillary tube, closely fitting into the axial bore of the sleeve, is fitted around an extremity of the fiber stripped of its protective sheath so as to extend close to the source when the two rings are substantially coaxially juxtaposed; with the source energized, the light emitted at the opposite fiber end is measured to determine the correct alignment position in which the two rings are cemented to each other.

Abstract: A switching unit for the selective transfer of bytes concurrently arriving in successive time slots over eight incoming signal paths to as many outgoing signal paths with intervening temporal and/or spatial transposition comprises a byte memory loaded by way of a series/parallel converter and read out by way of a parallel/series converter; two 8.times.8 storage matrices may alternately serve as the two converters. A routing memory, connected via a logic network to a command unit such as a microprocessor, controls the transfer and may also block the readout from the byte memory under certain conditions, specifically during an initiation procedure or where the switching unit is one of several such units forming part of a larger switching or concentration structure. In response to particular instructions from the command unit, a single byte from an incoming path may be transferred to one or all of the outgoing paths.

Abstract: A signal receiver at the subscriber end or the exchange end of a telephone line loop, over which messages are transmitted in digitized form by a carrier with four possible phase positions representing as many two-bit combinations or dibits, includes a coherent phase demodulator in which samples of the incoming carrier (converted to a square wave) are logically multiplied with coincident samples of a locally generated reference wave of like or subharmonically related frequency to produce a binary sequence of a configuration depending upon the relative phase.

Abstract: To decode multifrequency dialing signals transmitted by a pushbutton-equipped subscriber station of a telecommunication system and quantized upon arrival at a central office, a receiver at the office includes two digital filters separating the incoming binary-coded samples from sine waves in a higher and a lower frequency range and supplying the respective sets of samples to two interpolators converting them into respective square waves fed to a decoder. Each interpolator comprises a sign-bit extractor and an arithmetic unit which emits a numerical value--based on the absolute values of two consecutive samples--representing a delay expressed as a number of clock pulses recurring at a multiple of the sampling rate.

Abstract: A stream of digital symbols with three or more distinct amplitude levels, organized in a recurrent frame of N symbol periods, carries supplemental information in the form of a binary word of k bits per frame, with k substantially less than the probable minimum number of modulable waveforms, i.e. symbols of the lowest or the highest normal level. At a transmitting end of a signal path, the binary word is superimposed upon a group of k consecutive modulable waveforms at the beginning of each outgoing frame, with bits of logical value "1" indicated by a supermodulation of corresponding modulable waveforms to raise or lower their amplitudes to an extra-high or an extra-low level; the first and the last bit of this word have invariably the value "1". At a receiving end, a cyclic counter CL.sub.4 stepped by extracted clock pulses establishes a recurrent incoming frame of normally N symbol periods while a dead-end counter CC.sub.

Abstract: A binary input signal S multiplied by a level-controlling modifier X.sub.n-1 is periodically sampled to determine its amplitude whose value is then differentially combined with a fixed reference value R to produce an error signal. The latter is multiplied by the same modifier X.sub.n-1 and by a fractional coefficient k to yield a corrective value which is then algebraically combined with modifier X.sub.n-1 to produce an updated modifier X.sub.n for the next sampling cycle. To avoid instability, the modified input signal may be subjected to a limitation of its dynamic range before or after sampling. A load to be driven by the input signals may receive the modified signal itself or the modifier used to control its level.

Abstract: A signal-processing system, e.g. for a telephone exchange, comprises n modular processing units each including a pair of identical microprocessors operating in parallel on binary signals arriving over an internal bus, only one microprocessor of each pair being enabled to transmit outgoing messages to that bus while the other operates as a dummy. The two microprocessors are interlinked by a correlating connection enabling verification of their correct operation in response to microinstructions read out from respective microprogram memories thereof under the control of a common clock. A momentary divergence, resulting from a relative lag in the response of one microprocessor to an asynchronously arriving signal bit, results in a delay of the microprogram by one clock cycle to permit resynchronization; longer-lasting disparities lead to a deactivation of the microprocessor pair and to the emission of an alarm signal.

Abstract: A generator of ringing signals at a subscriber station of a telecommunication system, designed to respond to electromechanically generated lower-frequency call signals of large amplitude as well as to electronically generated higher-frequency call signals of small amplitude emanating from a central office, comprises a signal identifier and a level discriminator connected in parallel to an incoming line. The signal identifier includes a local oscillator emitting a train of pulses at a cadence substantially higher than any call-signal frequency which, in the presence of an incoming signal, are fed to a pulse counter during alternate half-cycles of a square wave derived from that signal.

Abstract: A system for measuring and storing the amplitudes plus duration and/or rise times of overvoltage pulses occurring on a transmission line comprises a voltage divider working into a first and a second comparator respectively detecting an abnormal voltage exceeding a predetermined sensitivity threshold and discriminating among different amplitude levels above that threshold. The first comparator triggers an oscillator driving a pulse counter which measures the duration of an overvoltage pulse and also provides quantized information on rise time to the highest amplitude threshold surpassed by that pulse as determined by the second comparator. This information is stored in a memory with two groups of cells respectively assigned to combinations of amplitude with duration and combinations of amplitude with rise time, the occurrence of any such combination incrementing the contents of the respective cell.

Abstract: An analog signal sent from one telephone subscriber to another is periodically sampled at a transmitting terminal and each sample is held for a storage period equal to a sampling interval as well as to a basic pulse period of a random or pseudorandom sequence of bipolar binary pulses. A stepped wave formed from these samples is mixed with that pulse sequence before being conveyed, e.g. by frequency modulation, to a receiving terminal where the wave so distorted is mixed with a like pulse sequence to re-establish the undistorted wave which may be contaminated by interferences from other users of the same signal link. The steps of the re-established wave are integrated over periods equal to the sampling interval and the integration products are stored for like periods to produce a purged stepped wave from which high-frequency components are subsequently filtered out to restore the original analog signal. The signal link utilized may be an emergency channel made available, e.g.

Abstract: A circuit arrangement for emitting ringing signals to a subscriber station in response to a call signal electronically generated at a telephone exchange comprises a control unit which, in the presence of such call signal, intermittently reverses a switching relay normally connecting the talking conductors of the subscriber line to monitoring equipment of the exchange whereby these conductors periodically receive a high-voltage ringing current, e.g. of 25 Hz, from a local oscillator in series with a d-c supply. The direct current is blocked by a line-terminating capacitor until the called subscriber lifts the receiver off the hook to close the line loop. If this occurs while the line is connected to the oscillator, a sensor in the control unit detects a significant disparity between the durations of the positive and negative voltage swings in an oscillator cycle and causes the release of the switching relay when that disparity exceeds a dynamic threshold determined by the actual cycle length.

Abstract: Light from a laser, converted into pulses by a chopper, is trained upon an end of an optical fiber--whose refractive-index profile is to be determined--through a first polarizer, a beam splitter, a focusing objective and a 90.degree. phase shifter, the space between the objective and the fiber end being occupied by a fluid whose refractive index is close to that of the fiber. Light reflected from the fiber end, having passed twice through the phase shifter, has a plane of polarization orthogonal to that of the incident light and is passed by a second polarizer, to which it is directed by the beam splitter, onto a photodiode feeding a calculator that also receives a reference signal from another photodiode to which part of the polarized laser pulses are directly reflected by the beam splitter. Spurious reflections from the objective surface, which do not pass through the phase shifter, retain the original polarization and are rejected by the second polarizer.

Abstract: An analog signal sent from one telephone subscriber to another is differentiated at a transmitting terminal and the resulting derivative is distorted by mixing with a random or pseudorandom sequence of bipolar binary pulses before being conveyed, e.g. by frequency modulation, to a receiving terminal where it is mixed with a like pulse sequence to re-establish the undistorted derivative signal with substantial suppression of interferences from other users of the same signal link. The re-established signal is integrated over intervals equal to a basic pulse period of the binary sequence and each signal sample thus obtained is additively combined with the sample from the immediately preceding period to restore the original analog signal. The signal link utilized may be an emergency channel made available, e.g. for communication with a mobile station, when regular channels are busy.

Abstract: An apparatus for handling incoming signals from sensors monitoring the state of certain points of a telephone circuit as well as outgoing signals for drivers associated with other circuit points includes a preprocessor PE inserted between the assembly DR of sensors and drivers, on the one hand, and a processor EL, on the other hand. The preprocessor and the processor have access, through a bus 5, to a common memory ME having areas allocated to the scanning of the circuit points, to time-counting operations and to the storage of messages from the preprocessor. A microprogram memory in the preprocessor, when addressed by a sequencer CM started automatically, manually or in response to an instruction from the processor, initiates a temporary seizure of the bus--if the latter is available--whereupon an initial address is delivered from the common memory ME to a working memory ML in the preprocessor to start the scanning of successive pairs of circuit points.

Abstract: A digitally operating telephone exchange, especially one serving an area of low subscriber density, comprises a multiplicity of control units of substantially identical structure programmed to carry out different functions in the establishment and termination of communication among associated subscriber stations. The several control units communicate with one another, and with the subscriber stations, through a common PCM coupling network with the aid of an access unit also having a similar structure. One control unit dialogues with a higher-ranking central office for communication with subscriber stations outside the area served by the exchange.

Abstract: A device for analyzing the quality of digital speech-transmission equipment, specifically a speech coder, comprises generators of white-noise signals, sinusoidal signals, frequency-shaped signals and artificial speech-like signals connected to the coder and to an adaptive transversal filter in parallel therewith. The filter and the coder feed output signals to a subtractor which produces an error or noise signal by deducting digital samples of the filter output signal from corresponding samples of the coder output signal. The error signal is fed back to the filter during a first testing phase to control the periodic modification of weighting coefficients computed by a multiplicity of updating cells in the filter for multiplicative combination with incoming samples of the test signal. The first phase ends when the coefficients converge to fixed values representative of the linear characteristics of the coder and the error signal assumes a substantially constant near-zero level.

Abstract: To facilitate determination of the refractive-index profile of an optical fiber by the near-field technique, the fiber to be examined is inserted into a body of transparent liquid held by surface tension in a surrounding capillary tube also made of light-transmissive material. The tube, which is axially coextensive with the inserted fiber, has a refractive index less than the minimum index of the fiber core and cladding whereas the liquid has a refractive index exceeding the maximum index of the fiber core.

Abstract: A central processor controlling a set of peripheral units through an associated logic network is programmed to activate from time to time, through a direct connection by-passing the logic network, a checking unit including a read-only memory storing a variety of microprograms in areas individually addressable by the processor. Upon the reception of a memory address, a timing circuit is set to determine the frequency of stepping pulses advancing a counter which calls forth successive phases of the selected mircroprogram. Code words read out during these phases to the logic network are fed back by the latter to the processor for comparison with corresponding contents of its own program memory; in the event of a disparity, or when failure of the processor to emit a resetting signal lets the counter advance to the limit of its capacity, an alarm indicator is tripped.

Abstract: In order to provide an end face of an optical fiber with a spherical curvature of predetermined radius, designed to optimize the transfer of luminous intensity from an adjoining light source such as a light-emitting diode, a flat fiber is heated to a temperature near its melting point while its profile is optically enlarged. When that profile is found to have reached a predetermined shape criterion, as determined by visual observation or by electronic scanning, heating is terminated.

Abstract: A microprocessor associated with a PCM telecommunication network dialogues with remote data-handling components such as other microprocessors through message-interchange circuitry which includes a read/write memory having storage areas individually allocated to several PCM channels, one storage area serving to receive incoming messages destined for the local microprocessor while the remaining storage areas serve for the transmission of outgoing messages intended for respective remote components. A control unit, timed by signals from a synchronization extractor coupled to the network, communicates with the memory to detect state words written by the microprocessor into the memory to indicate the loaded or vacant condition of its storage areas.