| 摘要 |
<p>PURPOSE:To eliminate the need for a new tone oscillator to send an alarm signal and to obtain accurate information with a simple method at a signal reception section by utilizing a measurement use low frequency signal voltage applied to an electronic line for measuring an insulation resistance for the data transmission, using plural carriers and adding demodulated outputs. CONSTITUTION:An output of a synchronization detector 8 of an insulation resistance measurement device is converted into a digital signal at an A/D converter 20, multiplexed with other measurement data fed from an external input terminal 31 as required at a multiplexer circuit 21, the result is fed to a low pass filter 22, in which the signal is shaped. The data are modulated by each carrier fed from a frequency divider circuit 19 and the result is sent to a line together with a measurement use low frequency signal. On the other hand, the measurement use low frequency signal extracted at the receiver side is used to generate a demodulation use carrier signal and sent data are demodulated. Moreover, since noise is reduced by adding demodulation outputs with respect to carriers, then the S/N of demodulation output is improved.</p> |
