Abstract: A multi-superheterodyne receiver having a first local oscillator for generating a first local frequency signal, a first frequency converter for converting to a first intermediate frequency signal a received signal in response to the first local frequency signal, a second local oscillator for generating a second local frequency signal, a second frequency converter for converting to a second intermediate frequency signal the first intermediate frequency signal in response to the second local frequency signal, includes judging circuitry for judging if a residual spurious component is generated when harmonic waves of at least one of the local frequency signals are at certain frequencies.

Abstract: A measured signal is supplied to an indication section through a high-frequency amplifier, a frequency converter, and an intermediate frequency amplifier. A predetermined local oscillation signal from a local oscillator is supplied to the frequency converter. A reference signal generator generates harmonic pulses having a uniform level at a spectral interval substantially equal to or larger than the predetermined passband of the intermediate frequency amplifier, the uniform level being used to calibrate a level of the signal to be measured. A frequency setting section sets the frequency of the measured signal. A first switching section switches an input to the high-frequency amplifier to an output side of the reference signal generator in accordance with the frequency set by the frequency setting section.

Abstract: A microwave oven comprises a digital control circuit for controlling microwave generation, and a multi-digit digital display unit for displaying a cooking condition. A determination system is associated with a door switch for developing a display control signal when a cook start switch is actuated before an oven door is tightly closed. In response to the display control signal, an alarm display, for example, "DOOR" is provided on the multi-digit digital display unit. The microwave oven further comprises a food temperature sensor probe for sensing a temperature of foodstuff being cooked. The multi-digit digital display unit provides another alarm display, for example, "PROBE" if the cook start switch is actuated under the condition where the food temperature sensor probe is not placed in its operative condition even though the food temperature control mode of operation is selected.