Abstract: A helical UHF transmitting and/or receiving antenna for electromagnetic waves in the frequency range of between 400 MHz and 1000 MHz. The helical antenna is arranged within a closed housing which is permeable to HF radiation. The UHF signal is supplied to an end of the helical antenna through a coaxial connector. The helix of the antenna has at least one and a half turns but not more than ten turns. Diameter, height and total length of the antenna wire are very small in comparison to the wave length. A mechanically-operated device permits a continuous change of the height of the antenna helix in axial direction thereof or of the diameter transversely of the antenna axis.

Abstract: In a device for producing artificial reverberation by means of a one-dimensional waveguide, a one-dimensional waveguide is utilized, which is obtained using digital circuits which contain at least two line sections of different length, each line section consisting of two parallel digital delay arrangements, one for each direction of propagation. At least one three-gate adapter of the digital wave filter type is arranged between two line sections lying side by side, each of two gates of the three-gate adapter being connected with one of the two mutually facing ends of these two line sections, and the dependent gate of the three-gate adapter being terminated with a frequency-dependent absorber of the digital type. By using a digital one-dimensional waveguide with discontinuities and absorbers, it is possible to reverberate a signal diffusely and with a programmable frequency response of the reverberation time without the disadvantage of a reduced sound to noise ratio due to limit cycles.

Abstract: The invention concerns a firing device for a number of electric valves, particularly thyristors. Each thyristor control path is associated with a firing circuit with a detector for electromagnetic radiation responsive to a transmitter which is controlled by a firing control signal and is equipped with a radiating device which energizes the individual detectors. To transmit the firing control signal with sufficient strength, a transmitter with a radiator is provided which is arranged in the focal line of a reflector designed as a partial elliptical cylinder. The individual detectors are disposed in a line which is aligned essentially parallel to the focal line of the reflector.

Abstract: A circuit arrangement for the wireless transmission of a control signal to the control path of a semiconductor valve. In particular, the circuit arrangement is provided with a separating filter which is connected to a remote-indication receiver and which is arranged between the high-frequency transmitter and the transmitting antenna of the circuit arrangement. Specifically, the filter includes two directional couplers which are separated by a distance equal to one-eighth of the wavelength of the carrier frequency transmitted by the high frequency transmitter.

Abstract: The invention concerns a circuit arrangement for the wireless transmission of control signals to the control paths of controlled semiconductor valves, particularly of thyristors, which are preferably usable in a rectifier for high voltage. The control signals are provided for the modulation of a high-frequency transmitter which is disposed at some distance from high frequency receivers each containing a demodulator, whose output signal is delivered to the control path of a semiconductor valve. In order to ensure reliable and interference-proof firing of the semiconductor valves, if the distance between the high-frequency transmitter and the high-frequency receiver is large, there is provided, a frequency-modulated high-frequency transmitter as the high-frequency transmitter.