Abstract: Pterin derivatives are described having the formula (I) ##STR1## wherein R represents a hydroxyphenyl group, a radioiodinated hydroxyphenyl group, a tyraminocarbonyl group, a radioiodinated tyraminocarbonyl group, a proteinocarbonyl group or a carboxy group; Q represents a straight or branched chain alkylene group having 1 to 6 carbon atoms; and R.sub.6 and R.sub.7 each represents a hydrogen, an alkyl group having from 1 to 6 carbon atoms, a hydroxyalkyl group having from 1 to 6 carbon atoms; and a radioimmunoassay method is described using a radioiodinated 4-hydroxy-2-tyraminopteridine derivative or a radioiodinated 4-hydroxy-2-tyraminocarbonylalkylaminopteridine derivative as the tracer.

Abstract: Abnormal separation detecting circuit of chromatic signals transmitted by a SECAM system comprises a detection circuit which receives a chromatic signal made up of R-Y signals and B-Y signals respectively added with identification signals I.sub.1 and I.sub.2 at their front ends for detecting the identification signals I.sub.1 and I.sub.

Abstract: An oscillator comprising an oscillation circuit including an oscillation transistor whose emitter is connected to the ground with respect to a D.C. signal; a detection circuit for detecting D.C. power source current supplied to said oscillation transistor; and a control circuit for controlling a D.C. bias voltage impressed on said oscillation transistor according to an output signal from the detection circuit, wherein the oscillation circuit, detection circuit and control circuit jointly constitute a negative feedback loop for sending direct current back to the source.

Abstract: An automatic gain control circuit includes a first transistor whose base is supplied with an input signal and whose collector is impressed with a first source voltage through a first resistor and a second transistor whose collector is connected to the emitter of the first transistor, whose emitter is grounded and whose base is impressed with an automatic gain control voltage. The collector of the first transistor serves as an output terminal of the automatic gain control circuit. The automatic gain control circuit further includes a third transistor whose base is connected to the base of the second transistor and whose emitter is grounded and a fourth transistor whose emitter is connected to the collector of the third transistor, whose collector is connected to the base of the first transistor through a second resistor and is impressed with a second source voltage through a third resistor and whose base is connected to said collector through a fourth resistor.

Abstract: A Hartley oscillator includes a basic Hartley oscillation circuit having a semiconductor active element, a tank circuit coupled to the active element and having a grounded end, a coupling capacitor connected between the other end of the tank circuit and a control electrode of the active element. A constant direct current source for supplying a constant direct current to an electric current supply terminal of the active element is further provided. A feedback circuit is coupled to the active element and the output of the constant direct current source and adapted to cause a variation of a direct current potential on the current supply terminal of the active element to be fed back to the control electrode of the active element, and a capacitor having a grounded end and the other end connected to the output of the constant current source is further provided in the Hartley oscillator.