Abstract: A recording/playing circuit includes a noise reduction circuit, a switching circuit and a control circuit. The noise reduction circuit includes a pre-amplifier, a combining network, an inverter circuit and a side chain. The switching circuit has first, second and third input positions and an output terminal. The first input position is coupled to the output of the pre-amplifier, the second input position is coupled to the output of the inverter circuit, and the output terminal is coupled to the side chain. The third input position is connected to a muting circuit. The control circuit controls the switching circuit so that one of the electric signals applied to the first, second and third input positions of the switching circuit may be selectively transmitted to the output terminal of the switching circuit.

Abstract: The cut-off frequency of a transistor drops remarkably when the collector-emitter voltage of the transistor is driven into the quasi-saturation region of about 1 V. To prevent this problem, the collector-emitter voltage of the transistor is detected and compared with a predetermined reference voltage by comparison-limiting means. The comparison-limiting means limits the base current of the transistor and thus restricts the drop in the collector-emitter voltage. Limiting the voltage drop in this manner prevents the transistor from being driven into the quasi-saturation region. The reference voltage is set to the p-n junction voltage in the forward direction. Hence, the drop in the collector-emitter voltage is limited to a value near this reference voltage.

Abstract: A selecting information for adjusting the frequency-dividing ratio of a programable divider in a PLL synthesizer tuner is stored in the memory.In order to prevent the same selecting information from being written down in the different addresses in the memory, all of the selecting informations already written down in the memory is compared with the selecting information that is to be written down by a comparator circuit before the selecting information is written down in the memory. The output of the comparator circuit permis the selecting information to be written into the new addresses only when the selecting information that is to be written down is different from all of the selecting informations which have been written down already.

Abstract: A mixture of anion and cation exchange resins is separated into their respective resin types by classifying the resin mixture, using a fluid such as water, in the presence of a solid, inert material (e.g., copolymer beads of styrene, divinylbenzene and methyl methacrylate) which, upon classification, forms a layer intermediate between the layers of the anion and cation resins. The degree of resin separation and the location of the layers of the classified anion resin and cation resin are determined by measuring a conductivity property of the resulting classified resin bed.

Abstract: An aircraft landing-guiding apparatus having an antenna system constituted by a plurality of antenna elements arranged in a line and intersecting the course of a runway substantially at right angles at the lengthwise center of the runway.Phases of sideband signals and carrier signals are shifted at rates having such relationship that sideband patterns and carrier patterns are sent forth from the antenna system at prescribed horizontal angles to the course of the runway.