Abstract: The invention provides a small-sized low-cost spread spectrum communication device including a narrow-band interference signal elimination circuit capable of covering all the frequency band of a spread signal. A spread signal is received by an antenna and supplied to a level detection circuit via a variable amplifier and a divider. The level detection circuit controls the variable amplifier so that the spread signal is amplified to a fixed level. The signal containing a narrow-band interfering signal is then passed through a plurality of magnetostatic filters connected in series such that the saturation level thereof successively decreases, thereby limiting the narrow-band interfering signal having a level greater than the level of the spread signal in a step-by-step fashion. Thus, the narrow-band interfering signal contained in the spread signal is limited to a low level without encountering a significantly large incidental reduction in the spread signal.

Abstract: An S/N enhancer is provided which can be formed to be small in size and in which impedance matching can easily be achieved. The S/N enhancer includes two magnetostatic wave elements. First to fourth transducers each in the shape of a single line are disposed on YIG thin films of the magnetostatic wave elements in parallel and spaced from one another. An input terminal is connected to one end of the first transducer. An attenuator is connected between the other end of the first transducer and one end of the third transducer. A 180.degree. shifter and another attenuator are connected in series between one end of the second transducer and one end of the fourth transducer. An output terminal is connected to the other end of the fourth transducer. The other ends of the second and third transducers are respectively grounded.

Abstract: A compact, low-cost magnetostatic wave device which can serve as an S/N enhancer or a filter. The magnetostatic wave device includes a ferromagnetic base; at least one transducer having a portion arranged adjacent to one surface of the ferromagnetic base and another. portion arranged adjacent to the other surface of the ferromagnetic base; an input terminal with one side connected to one end of the transducer and the other side grounded; and an output terminal with one side connected to the other end of the transducer and the other side grounded. The ferromagnetic base is preferably disk-shaped.

Abstract: A magnetostatic wave device includes a dielectric substrate. Micro strip lines as transducers are formed by forming a ground electrode and strip-line electrodes, on both surfaces of the dielectric substrate. A ferrimagnetic base material formed with a GGG substrate and a YIG thin film on the GGG substrate is arranged on the strip-line electrodes. The ferrimagnetic base material is formed so that the end portions slant from the strip-line electrodes outwardly. The length of the ferrimagnetic base material is established to provide a minimum value.

Abstract: A signal-to-noise enhancer 10 includes a first 90 degree hybrid set 20. A first output end of the first 90 degree hybrid set 20 is connected to an input end of a limiter used a magnetostatic wave element 62a utilized the magnetostatic surface wave mode. Also, a second output end of the first 90 degree hybrid set 20 is connected to an input end of a filter used a magnetostatic wave element 62b similar to the magnetostatic wave element 62a in structure, via a resistor 32 as a first attenuator. Furthermore, an output end of the limiter is connected to a first input end of a second 90 degree hybrid set 40 via a resistor 52 as a second attenuator. Also, an output end of the filter is connected to a second input end of the second 90 degree hybrid set 40.

Abstract: A magnetostatic wave resonator includes a YIG thin film. On one main surface of the YIG thin film, three circular conductors having different radii are disposed on concentric circles whose centers are the center of the YIG thin film. Furthermore, on the YIG thin film, two transducers are disposed so as to intersect with each other at right angles at the center of the YIG thin film and to connect magnetically to the YIG thin film.

Abstract: The magnetostatic wave device 10 includes a holder 12 made of synthetic resin. The holder 12 is provided with a number of recesses 14, 16, 22a, 22b, 24a and 24b. In the holder 12, a magnet 30 is housed in the recess 14, and a YIG element 32 as a ferromagnetic element is housed in the recess 16, and transducers 34a and 34b are housed in the recesses 22a, 22b, 24a and 24b.

Abstract: A fire alarm apparatus includes a fire receiver, a pair of transmission lines extending from the fire receiver, a series of nonpolar fire detectors connected to the transmission lines, and a terminating unit, connected to the end terminals of the transmission lines, the terminating unit having an impedance element including a polar element. Each fire detector includes polarity inverting circuitry which includes a limit switch, arranged at a socket portion of the detector, and having a switch lever which is actuated by the detector body engaging with the socket portion; and diodes for inverting the polarity of the pair of transmission lines in synchronism with actuation of the switch lever. The polarity of the transmission lines after a detector is inverted when a detector body is detached from that detector.

Abstract: An input video signal is fed to a substracter wherein a difference is taken between the input and the output from a frame memory to provide a difference signal, the magnitude of which is controlled by a magnitude adjuster. The controlled output is then fed to a threshold circuit, from which a significant difference signal is derived which has a magnitude above a given level. The significant difference signal is quantized by an encoder into a code having a reduced number of bits as compared with the inputted significant difference signal. The quantized code is written into a buffer memory, and is read out therefrom at a uniform bit rate to a transmission line. A sum of a signal indicative of the representative level of the quantized code from the encoder and the output of the frame memory is formed in an adder, and the sum signal is written into the frame memory and read out subsequently or after one frame.

Abstract: In interframe coding apparatus in which an input signal is encoded by an interframe coder and its output code is written in a buffer memory, and is read out therefrom at a constant bit rate, a variable characteristics comb filter is provided at a stage preceding the interframe coder. The period of the frequency characteristics of the comb filter is selected to be the frame period of the input signal. By a controller, the occupancy of the buffer memory is detected to control either one or both of the attenuation in the elimination band and high frequency cut-off characteristics of the comb filter detected value to prevent an overflow from the buffer memory.