| 摘要 |
PURPOSE:To detect the locked state of a phase synchronizing oscillator in an indoor device by providing a current consumption varying circuit which varies a current to be consumed at a converter corresponding to the locked state of the phase synchronizing oscillator used in the converter, and detecting the change of the current in the current change detection circuit of the indoor device. CONSTITUTION:The phase synchronizing oscillator 6 outputs a low level when the locked state is set, and a high level and a DC voltage corresponding to the locked state to a lock detection signal output terminal 12. The current consumption varying circuit 13 connected to the phase synchronizing oscillator 6 is provided with a function to increase current consumption when the DC voltage level of a lock detection signal is set at the high level compared with a case when it is set at the low level. In the indoor device 2, the current change detection circuit 18 provided between a power source circuit 16 and an inductance 17 detects the change of the current on a coaxial cable 3, and assumes that the phase synchronizing oscillator 6 in a lownoise converter 1 is set in an unlocked state when the change shows a value exceeding a current value set in advance, and outputs an unlock signal to a lock detection output signal 19. |
