Abstract: A ceramic heater for a DC power source comprising an insulating ceramic sintered body, a heating resistor composed of at least two separate layers of heating resistor made of an inorganic conductive material, leads made of high-melting point metal wires and connected to each end of the layers, and electrodes made of an inorganic conductive material, each formed in a single layer or divided into a plurality of pieces and connected to the leads, the heating resistor, leads and electrodes being embedded in the ceramic sintered body.The present invention further includes six related inventions closely related with one another in regard to the above-mentioned ceramic heater and ceramic glow plugs embodied by using the ceramic heater.

Abstract: Band pass filter circuit for a band pass filter which detects a phase difference between input and output signals of said band pass filter, and the detected output controls, via a low pass filter, a voltage controlled oscillator, the output of which controls first and second mixers connected respectively to an input side and an output side of the band pass filter, so that the output of the first mixer can be maintained at the center frequency of said band pass filter. Further, when an irregularly timed signal is received, before an input signal is pulled in the synchronized state, said band pass filter is provided with a wide pass band so as to pull the signal in the synchronized state in rapidly.