| 摘要 |
<p>Data is transmitted on a power line (15) as a momentary interruption of the power at or near the zero crossing of the current. The interruption is preferably a small fraction of the period of the frequency of the power line. The data is transmitted only to those devices in series circuit with the transmitter. The transmitter (13) combines 60 Hz and 120 Hz clock signals with data from a shift register to interrupt current in a predetermined pattern, in which an interruption of both the positive going and negative going zero crossings define a logic '1' and the absence of interruptions is a logic '0'. A data prefix identifies succeeding bits as data. The receiver (17) produces a pulse width modulated signal in response to the data.</p> |
