Abstract: A signal discrimination circuit judges whether an input signal contains a control signal or not, the control signal having a specific frequency and a specific level for a specific time duration. The signal discrimination circuit includes a component power detection device for detecting the power of a component which is in the input signal and having the specific frequency and a level judging device for determining whether the power of the component is equal to or greater than a power reference value. Finally, a control signal judging device is included for determining that the input signal includes the control signal, when the level judging device judges that the power of the component is equal to or greater than the power reference value, continuously for the duration of a reference time.

Abstract: A superconducting element is disclosed which includes a substrate and a superconducting layer provided on the substrate and formed of an oxide having the following chemical formula:RBa.sub.2 (Cu.sub.1-x M.sub.x).sub.3 O.sub.7wherein R represents at least one element selected from the group consisting of Y, La, Nd, Pm, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu, M represents at least one element selected from the group consisting of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Zn and Ga, and x represents a number of less than 1 but greater than 0.

Abstract: A phase shift angle detector for detecting a phase shift angle of a multiphase modulated signal includes a first multiplier coupled with a first low pass filter for producing a cosine wave signal having a phase which is a sum of a phase shift .phi.e and the modulated signal g(t), and a second multiplier coupled with a second low pass filter for producing a sine wave signal having a phase which is a sum of a phase shift .phi.e and the modulated signal g(t). A circuit is provided for calculating an inverse tangent using the cosine wave signal and the sine wave signal to produce a signal representing the pahse shift .phi.e.