Abstract: A signal input selecting circuit comprises a plurality of signal input terminals, a first switch device for selecting one of signal electrodes of the signal input terminals to be connected with a signal processing block, a second switch device for selecting one of reference electrodes of the signal input terminals to be connected with a reference potential point, a third switch device for connecting the second switch device with a current supplying portion, and a voltage detector for detecting a voltage corresponding to an impedance of the second switch device.

Abstract: An apparatus for providing electromagnetic shielding. A wire for carrying an electrical signal is shielded with a first cylindrical ferrite shield by passing the wire through its central passage. The first ferrite shield has magnetic characteristics which provide attenuation of electrical noise over a first particular frequency band. A second cylindrical ferrite shield is situated adjacent the first shield with the wire passing through its central passage. The second ferrite shield has magnetic characteristics which provide attenuation of electrical noise over a second particular frequency band. A plastic package surrounds the first and second ferrite shields, and holds the first and second shields end to end in fixed proximity to one another. The plastic package includes a pair of half-cylindrical package sections having a joined edge and two open edges with a hinge portion joining the pair of package sections at the joined edge.

Abstract: A high frequency PIN diode attenuator uses an inductive element in parallel with the PIN diode. The inductor resonates with the parasitic capacitance of the PIN diode to increase the attenuation level.

Abstract: A PLL Frequency Synthesizer includes a reference signal source which outputs a reference frequency signal. A phase of the signal out of the reference signal source and a phase of a signal coming back through a feed-back loop are compared by a phase comparator which detects the phase difference between them. The output of the comparator is integrated by a low pass filter which generates a voltage output corresponding to the phase difference. A voltage controlled oscillator is also provided to the PLL Frequency Synthesizer of the invention, an output frequency of which is controlled by the amplitude of a signal out of the low pass filter. The output signal out of the voltage controlled oscillator is divided by a variable divider whose denominator can be variable from outside. A frequency multiplier is provided between the phase comparator and the variable divider so as to multiply the frequency of signal derived from the variable divider.