Abstract: A data transmission system utilizing a power line comprises a transmitter (1), a receiver (2) and a repeater (5) coupled to a power line (3). Control data including a start code in the form of a high frequency signal is transmitted from the transmitter (1) in superposition on an alternating current of the commercial power supply using the power line. The repeater receives the control data transmitted from the transmitter, thereby to store the control data in a memory responsive to the start code. The control data is then read from the memory after the lapse of a predetermined period of time and is retransmitted to the receiver in a predetermined level. The receiver receives the control data, thereby to control an apparatus being controlled such as a relay, whereupon the same transmits in a return manner the data representing a control state thereof. The repeater receives the data and transmits the same to the transmitter.

Abstract: A data transmission system utilizing a power line comprises a transmitter (1), a receiver (2) and a repeater (5) coupled to a power line (3). Control data including a start code in the form of a high frequency signal is transmitted from the transmitter (1) in superposition on an alternating current of the commerical power supply using the power line. The repeater receives the control data transmitted from the transmitter, thereby to store the control data in a memory responsive to the start code. The control data is then read from the memory after the lapse of a predetermined period of time and is retransmitted to the receiver in a predetermined level. The receiver receives the control data, thereby to control an apparatus being controlled such as a relay, whereupon the same transmits in a return manner the data representing a control state thereof. The repeater receives the data and transmits the same to the transmitter.

Abstract: A transmitter connected to any phase of a 3-phase alternating current transmits a data subsequent to a lock signal in synchronism with the cycles of the phase. A receiver connected to any phase of the 3-phase alternating current receives a lock signal in synchronism with the cycles of the phase. The receiver receives each data after the receiver is synchronized with the transmitter using the lock signal. The synchronized relation is maintained, that is locked until each data transmission subsequent to a lock signal is terminated. The lock is released upon detection of an end signal added to the last portion of each data or a non-busy signal interval. In the case wherein a data transmission is repeated a plurality of times, a set of signals including a lock signal and a data is repeatedly sent out, interleaved with a non-busy signal interval.