An electromagnetic drive system includes a motor having a first motor section movable relative to a second motor section along a motion axis. The second motor section has three excitation coils. The first motor section includes a magnetic circuit generating a magnetic field in the excitation coils. The first motor section also includes a short-circuit winding for only high-frequency induction currents. This short-circuit winding is magnetically coupled to the excitation coils. The degree of electromagnetic coupling of at least one excitation coil depends on the position of the first motor section relative to the second motor section. The short-circuit winding provides a position-dependent electromagnetic coupling between the center excitation coil and the two outer excitation coils. The position-dependent coupling can be detected by superimposing a high-frequency detection signal on the excitation system for the center coil and by detecting currents induced in the two outer coils by the high-frequency detection signal. Thus, a compact drive system with a built-in position detector is obtained.

The invention relates to an X-ray image detector, comprising a plurality of X-ray-sensitive sensors and having the following features: each sensor comprises a collecting electrode and a switching element which connects the collecting electrode to an output lead; a photoconductor layer is provided between the individual collecting electrodes and a bias electrode; the collecting electrodes form, in conjuction with reference electrodes, capacitances which can be charged by charge carriers generated in the photoconductor. The invention improves the effectiveness of such an X-ray image detector in that either the surface area of the collecting electrodes is increased or the electric field is distorted by a semiconductor layer so that the majority of the charge carriers generated in the photoconductor flow to the collecting electrodes.

Transmission system, and transmitter and receiver for use in the transmission system for transmitting and receiving digital signals containing modulated bit allocation information. The transmitter encodes a wide-band digital signal into subband signals which are each made up of successive signal blocks having a predetermined number of samples of that subband signal. The samples in the signal blocks of the subband signals are quantized to produce quantized samples in the signal blocks, and bit allocation information denoting how many bits the samples in the signal blocks are to be quantized by is generated. The bit allocation information (or a portion thereof) is modulated to obtain modulated bit allocation information. The quantized samples in the signal blocks and the modulated bit allocation information are included in a digital signal applied by the transmitter to a transmission medium. The receiver receives a replica of the digital signal applied to the transmission medium. The modulated bit allocation information is demodulated to obtain the bit allocation information. The quantized samples in the signal blocks and the bit allocation information are used to obtain replicated samples in the signal blocks which substantially correspond to the original samples in the signal blocks of the subband signals. The replicated samples are used to produce a replica of the original wide-band digital signal.

Optical amplifier which utilizes a solid-state laser as an amplifying element. In the optical amplifier, according to the invention, a linearity improvement is achieved by feeding the solid-state laser from a voltage source rather than from a current source, as is customary.