Abstract: A detector for a modulated AM stereophonic signal of simple configuration in which the sub signal of the stereophonic signal is detected accurately independent of fluctuations in the frequency of the carrier signal. In the detector circuit, the output phase of a VCO in a PLL circuit which is fed with an amplitude limited signal corresponding to the output of an IF amplifier in the receiver is controlled by a variable phase shifter that performs phase shifting according to a control voltage. The phase-controlled output is used as a synchronous detection signal for sub signal detection. The control voltage is produced to correspond to the phase difference between the phase-controlled signal and the carrier signal of the received AM stereophonic signal.

Abstract: A muting circuit for an AM stereophonic receiver of the type in which a received signal is phase modulated with a sub signal and amplitude modulated with a main signal and in which noise generated under certain adverse conditions is eliminated. A first detection signal is generated when the level of a received AM stereophonic signal is lower than a predetermined value, a second detection signal is generated upon detection of a non-locked state of a phase-locked loop circuit used to detect the sub signal, a third detection signal is generated when a frequency deviation detection senses is that a free-running frequency of a voltage controlled oscillator in the phase-locked loop circuit and a frequency of the AM stereophonic signal are different in frequency by more than a predetermined value; and a fourth detection signal is generated when a stereo pilot signal is absent. A muting circuit is activated in response to any of first through fourth detection signals.

Abstract: A phase control circuit for use in a compatible quadrature AM stereophonic receiver in which the phase of the output signal of a voltage-controlled oscillator in a phase-locked loop circuit has a fixed predetermined phase difference with respect to the input signal at all times. A variable phase shifter varies the phase of the output signal from the voltage controlled oscillator in the phase-locked loop circuit in accordance with an input control voltage. The phase of the output of the variable phase shifter is compared with the phase of the input intermediate frequency signal to produce a control signal voltage for the variable phase shifter which varies according to the phase difference between the two compared signals wherein the desired signal having a fixed phase difference is provided at the output of the variable phase shifter.

Abstract: In a current-controlled type division circuit, an auxiliary transistor is employed in conjunction with a division control transistor to allow a divisor signal, which normally flows through the division control circuit, to flow through the auxiliary transistor in the case when a division controlling signal applied to the base of the division control transistor falls below a predetermined level. By the provision of the auxiliary transistor, the divisor signal of a predetermined minimum is adapted to be flown therethrough to prevent the gain of the division circuit from exceeding a predetermined maximum.

Abstract: A development method which comprises imagewise exposing a positive acting light-sensitive planographic printing plate comprising an aluminum support and a light-sensitive layer of an o-quinonediazide compound formed thereon, and then developing the exposed plate with a developer, comprising an aqueous solution of an alkali metal silicate, adding a supplementary solution comprising an aqueous solution of an alkali metal silicate to the developer to compensate for the degradation of the developer brought about by development and/or by carbon dioxide in the air; wherein the developer comprises an aqueous solution of an alkali metal salt having an [SiO.sub.2 ]/[M] ratio of from 0.5 to 0.75 and an SiO.sub.2 concentration of from 1 to 4% by weight based on the total weight of the developer, where [SiO.sub.2 ] represents the concentration of SiO.sub.