Abstract: For recognizing the status of a "no light" condition at the signal input of a receiving terminal, measured values that correspond to the electrical signal level of received signals are stored at given time intervals. In the absence of digital signals, the contents of the memory, potentially in combination with a further measured value, are searched for a change in the amplitude of the received signal. Given a large level change, a "no light" condition is reported.

Abstract: Method for quality monitoring of at least two series connected transmission sections in a digital signal transmission link for digital equipment conforming to the synchronous digital hierarchy. Error message bytes in which parity errors are accumulated are transmitted in the section overhead of synchronous transport modules as special bytes for the accumulation of parity errors in successive transmission sections. A quality criterion for the monitored transmission link is acquired from a sequence of error message bytes. The method and the apparatus are advantageously used in transmission equipment of digital synchronous hierarchy.

Abstract: Method and apparatus for individually monitoring transmission sections of a communication transmission link, whereby auxiliary signals serving the purpose of bit error recognition are newly-calculated when they are regenerated. In order to be able to check monitoring circuits under remote control, the auxiliary signals in a test mode are formed in a manner different from that in a normal monitoring mode. The reception of a prescribed plurality of such auxiliary signals serves as criterion for the test mode.

Abstract: A differential pulse code modulation coder has a pair of series connected arithmetic units connected to the input of a quantizer, with the output of the quantizer connected through a first multiplier to an input of the second arithmetic unit, and the output of the quantizer connected through an adder and further multiplier to the second input of the first arithmetic unit, the second input of said adder being derived from the output of said second multiplier, whereby greater internal calculation speed is realized.

Abstract: An arrangement for transmission of television composite signals contains coders which convert luminance component Y, and chrominance difference components U, and V of a television signal into variable-length code words. These are interlaced in a multiplexer in pulse frames by assignment to fixed locations. At a receive side, a time-division multiplex signal formed is in turn separated in a demultiplexer. Decoders reconvert the variable-length code words into the Y, U, and V components. The luminance and chrominance components can be reliably separated at the receive side due to the assigning of fixed locations in the pulse frame, these components being reliable separated even when the word synchronization of the individual components is lost.

Abstract: A method for clock rate conversion of digitized television signals for the acquisition of a television signal having a prescribed processing clock rate is provided wherein the digitized television signal is band-limited, a clock rate conversion being subsequently undertaken. The television signal having a second clock rate is written into a memory 6 and is, in turn, read with the prescribed processing clock rate, whereby an unaltering plurality of data words corresponding to picture points is not output in every television line.

Abstract: A transmission system wherein PCM code words are converted into DPCM code words at the transmit side and are reconverted into PCM code words at the receive side. A DPCM coder comprising a respective quantizer for variable-length code words, a quantizer for code words having a fixed, below-average length, and a DPCM decoder comprising a code converter for variable-length code words and a code converter for code words having a fixed, below-average length are provided for this purpose. The type of conversion for the next PCM code word present at the input is selected after each conversion on the basis of the number of memory locations that still exist. This transmission system is suitable for data reduction, particularly of digital video signals.

Abstract: A high-speed difference pulse code modulation coder comprises a calculating unit for determining an estimated value, the calculating unit comprising a quantizer which is preceded by three subtractors and has a plurality of outputs for emitting various calculated values. The difference pulse code modulation signal is calculated in a plurality of consecutive steps by way of intermediate values for calculation of a difference pulse code modulation signal, only two calculating steps are required within one period of the pulse code modulation signal to be processed.

Abstract: A difference pulse code modulation ("DPCM") encoder for encoding and compressing digital data. This encoder includes a quantizer formed by a read-only memory (ROM). DPCM signal values to be quantized are supplied without a sign bit as addresses to the ROM; the code words read-out as data from the ROM in response to addresses represent the quantized DPCM signal values. The size of the ROM required for this purpose is reduced by limiting the DPCM signal values which are supplied as addresses to the ROM. The sign bit contained in the DPCM signal values is not supplied to the ROM but is added to the code words read-out of the ROM as quantized DPCM signal values. In addition, the DPCM signal values and also the code words read out of the ROM are rounded off by omission of the least significant bit.

Abstract: In an improved digital DPCM-coder having a high calculating speed, a second quantizer is provided which is supplied with a DPCM-signal determined in a calculating loop, and which emits from its output a quantized DPCM-signal multiplied by a prediction factor. With the improved coder, one calculating operation less is required, and the coder can process a higher PCM-data rate at a constant calculating speed of the components.