Abstract: System for controlling the duration of the time interval between the blocks of data transmitted by a computer 1. A channel 7 transfers the first block to be transmitted to a control unit 2 which sends same over a line 4 through a modem 3. When the block has been transmitted, the unit 2 signals the channel accordingly and receives therefrom a command specifying the duration of the time interval between the blocks. The unit 2 activates interval timing means and signals the channel 7 when the time interval has elapsed. The channel can then send the second block to the unit 2.

Abstract: A switching network includes electronic crosspoint switches for providing electronic connection or disconnection between two voice stations. Each station is connected to the network through a line transformer. When two stations are connected to each other, the voice path in the network includes the secondary winding of the 1st station transformer, a series of crosspoint switches, a middle junctor, a series of crosspoint switches, and the secondary winding of the 2nd station transformer. Each middle junctor includes a negative resistance circuit which introduces a negative resistance in series with the voice path, thus compensating for the series losses in the network, and two negative inductance circuits connected on both sides of the junctor in parallel with the voice path, to compensate for the parallel losses, especially those introduced by the line transformers.

Abstract: In a synchronous data receiver that includes a clock and an adaptive equalizer, a method and a device for effecting the initial adjustment of the clock during a turn-on period in the course of which the receiver is supplied with a known clock synchronization signal followed by a known equalizer training sequence. In accordance with the method of invention, the incoming signal is sampled and the samples so obtained are stored in a storage means. The synchronization signal and the beginning of the training sequence are successively detected. When the beginning of the training sequence is detected, the storage locations for the samples of the received synchronization signal are known and a control signal controlling the initial adjustment of the clock is derived from these samples, which are stored in predetermined locations in the storage means.

Abstract: This invention relates to automatic adaptive equalizers used in those data transmission systems which rely upon a double sideband-quadrature carrier (DSB-QC) modulation technique. The term DSB-QC modulation is used here in a broad sense and includes all systems wherein the transmitted signal can be represented by superimposing two amplitude modulated quadrature carriers. Thus, the term DSB-QC includes, in particular, phase-shift keying, amplitude phase-shift keying and quadrature amplitude modulation. More particularly, this invention relates to a method and a device for training an adaptive equalizer by means of an unknown data signal sent to the receiver, and is especially useful in a data transmission system configured as a multipoint network.

Abstract: An arrangement for separating disturbing ambient light from an optical data signal, comprising an interference filter (1), the passband of which matches the wavelength of the optical data signal, and further comprising two photodiodes which are so arranged that one photodiode receives the light (I.sub.S, I.sub.AT) transmitted through the interference filter, and that the other receives the reflected light (I.sub.AR). Adjusting means, e.g., in the form of a settable aperture (4) or an additional simple filter (5) are provided for adjusting the transmitted and reflected portions of the ambient light to each other. Output signal (S1, S2) of both photodiodes are subtracted from each other in compensation circuitry (6). This results in compensation of the ambient light components so that at the output a signal (SR) is available which depends only on the actual data signal (I.sub.S).

Abstract: A dynamic preselect interrupt priority circuit in which a plurality of adapters dynamically readjust priority until selected whereupon adjustment stops and the adapter having the highest interrupt and position priority is selected.

Abstract: Binary/ternary transmission process and device. Several trains of binary signals are time-multiplexed by using registers RG1 and SER to generate a first binary sequence L applied to an ENCODE unit which also receives a second binary sequence D and clock information CP. When the information of sequence L is at one binary level, the resulting signal is coded in bipolar code. When the information of sequence L is the other binary level, the resulting signal is coded in biphase code.

Abstract: A method and device which, in a receiver forming part of a data transmission system using DSB-QC modulation and wherein the transmitter generates a first sequence of successive carrier phase changes of 180.degree. taking place at the signaling rate 1/T followed by a second sequence of pseudo-random carrier phase changes of 0.degree. and 180.degree., with the first of these being a 0.degree. phase change, permit detecting the beginning of said second sequence. The received signal is filtered to extract therefrom its components at frequencies f.sub.1 and f.sub.2 defined asf.sub.1 =f.sub.c -1/2T f.sub.2 =f.sub.c +1/2Twhere f.sub.c is the carrier frequency.The components at frequencies f.sub.1 and f.sub.2 are combined to generate a signal S of frequency 1/T. The beginning of said second sequence is determined by detecting the instant at which the energy of signal S drops below its average value.

Abstract: A method and a device which, in a receiver forming part of a data transmission system using DSB-QC modulation, permit detecting the beginning of a pseudo-random sequence of symbols pertaining to a first set of two symbols when this sequence is preceded by a sequence of successive alternations between two symbols pertaining to a second set, with the first and second sets being such that the beginning of said pseudo-random sequence will initiate a reversal of the phase of the components of the frequency spectrum of said sequence of alternations. In accordance with the method of the present invention, the received signal is demodulated, the DC component of the demodulated signal is determined, and the energy of that DC component is measured. The time at which said energy drops below its average value is indicative of the beginning of the pseudo-random sequence. In accordance with one aspect of the invention, the DC component of the demodulated signal is determined by passing the signal through a lowpass filter.

Abstract: In a synchronous data transmission system wherein data transmission is achieved by modulating a carrier wave of frequency f.sub.c at the signaling rate 1/T, a method for determining the initial phase value by which the phase of the receiver clock is to be varied during an initial synchronization operation during which a synchronization signal, the spectrum of which includes two distinct lines at frequencies f.sub.1 =f.sub.c -1/2T and f.sub.2 =f.sub.c +1/2T, is transmitted comprising the steps of:(a) sampling the synchronization signal fed into the receiver at the rate 1/.tau. which is a multiple of the signaling rate, to provide a signal x(k.tau.) where k=a, 1, . . . ,(b) multiplying the signal X(.tau.) by itself to provide a signal s(k.tau.).(c) computing the coefficient C.sub.o, which corresponds to the frequency 1/T, of the discrete Fourier transform of signal s(k.tau.) from N samples thereof, the number N being determined from the resolution R=1/N.tau.

Abstract: A method and a device for training the equalizer of a receiver used in a QAM transmission system, by means of an unknown data signal, thereby enabling in particular said equalizer to be trained in the cases described above. In accordance with the method of the present invention, in a data receiver wherein, under normal operating conditions, the data is detected with respect to a first constellation, the equalizer is trained by detecting the data with respect to a second constellation which comprises fewer points than said first constellation and by adjusting the coefficients of the equalizer by means of an error signal produced as a result of the detection operation performed with respect to the second constellation.In accordance with a first embodiment of the present invention, the second constellation is comprised of those points of the first constellation that are farthest from its center.

Abstract: A voice signal is transmitted digitally at reduced bit rate by use of data compression. The original frequency components of a telephone band width of the voice signal sampled at 8 KHz and quantized with 12 bits are transformed into three parameters: SIGNAL data representing adaptive quantization for lower frequency (300-800 Hz) sub-bands; COEF data representing pre-emphasized parcor type coefficients for the higher frequency (800-3000 Hz) band; and, ENERGY data representing higher frequency short term energy level. The three parameters are multiplexed for transmission in binary-code form, thereby representing a recoding of the original binary-coded voice signals.

Abstract: In a satellite communication system using optical carriers the down link radiation beam pattern is limited to illuminating only the receiver sites for power economy. The transmitting laser's beam pattern is shaped in such a way that the intensity distribution at the earth surface is adapted to the geographical distribution of the receiving stations. A suitably prepared hologram or set of stacked holograms storing different beam patterns is interposed in the radiation path. The antenna characteristic may be varied by selecting a particular hologram. This is accomplished by changing the beam angle of incidence by remote control.

Abstract: A specialized processor capable of computing a sum of products S=.SIGMA..+-.Pi where every product Pi is the product of two n-bit complex operands Ai+j Bi, the multiplier, and Ci+j Di, the multiplicand, where j=.sqroot.-1. The processor includes an instruction storage, means for decoding instructions read out of said storage and for controlling the operation of the processor, a data storage, and a multiplication and accumulation unit which has two multiplier-accumulator devices and several buffers for storing the operands Ai, Bi, Ci and Di sequentially read out of data storage. The real part Ai and the imaginary part Bi of the multiplier are respectively applied to the Multiplier inputs of the multiplier-accumulator devices and the real part Ci of the multiplicand is applied to the Multiplicand inputs of the multiplier-accumulator devices, which simultaneously compute the products Ai Ci and Bi Ci.

Abstract: A receiver for a data transmission system employing the interleaved binary phase shift keyed modulation technique. The received signal is demodulated by means of an in-phase reference carrier and a quadrature reference carrier both of which are supplied by a clock and carrier recovery device, thereby supplying the in-phase and quadrature components of the signal. The sign of the sum of these components and that of the difference between them are selectively gated to the output of the receiver under control of the clock signal supplied by the clock and carrier recovery device. In this device, the frequency of the received signal is doubled and the signal thus obtained is modulated by the clock signal at half the signaling rate extracted from the received signal. This modulation operation yields a signal at twice the carrier frequency from which the in-phase and quadrature reference carriers are extracted.

Abstract: A PIN photodiode structure uses direct side entry into the I region, thus permitting the use of thicker P and N regions with a comparatively thin I region without sacrificing speed and results in more constant spatial distribution upon carrier generation and longer wave length devices with conventional speeds or smaller devices at faster speeds, and may be integrated on the same chip with associated circuits.

Abstract: In data processing systems of the type having a plurality of terminals connected by communication lines to a commmunications controller (CC) which assembles and manipulates the data from or to the terminals and one or more host central processing units (CPU's) to which the CC is connected by a number of channels, the CC will usually have a channel adapter unit (CA) for each channel and a processing unit to control the operations of the CC and to service the CA's in turn. It is necessary that the CA's be serviced with proper priorities to avoid unnecessary loss of information. An allocation of the proper priority is required where each CA can perform tasks of different urgency.The CC shown has four channel adapters communicating with four channels of the CPU's. All CA's can signal for an interrupt of the processor in the CC when CA service is needed. All CA's cause processor interrupts on the same interrupt level.

Abstract: A method of and apparatus for determining during an initial training period the initial values of the coefficients of a transversal equalizer in a data transmission system in which the transmission channel creates frequency shift. The received periodic training sequence is modulated by a time-domain window signal whose Fourier transform exhibits a relatively flat central peak and has comparatively low values in the vicinity of those frequencies which are a multiple of the inverse of the period of the transmitted sequence, and the discrete Fourier transform W.sub.k of the modulated signal is computed. The values of the coefficients of the equalizer are obtained by computing the inverse discrete Fourier transform of the ratio F.sub.k =Z.sub.k /W.sub.k, where Z.sub.k is the discrete Fourier transform of the transmitted sequence.