A control system comprises a load (3) having an operative unit (5), and a control device (2) for supplying AC power to the load (3) via a power line (4) and operating the operative unit (5). The control device (2) has interruption means (6) and transmission means (7). The load (3) has control means (10). The transmission means (7) transmits a predetermined control signal to the load (3) via the power line (4) by using the interruption means (6) to block the power supply to the load (3) for a time duration shorter than a half cycle of AC output. The control means (10) controls the operative unit (5) on the basis of a control signal received from the control device (2).
