DATA TRANSMISSION SYSTEM VIA POWER SUPPLY LINE

摘要

A data transmission system for transmitting data via a power supply line includes a central processing unit, and branch terminal units connected to the central processing unit via the power supply line, through which a high frequency AC signal is synchronously mixed into the AC commercial frequency power supply cycle so that a specific operation can be performed and the actual condition of the terminal units can be sampled and monitored during a normal operation. Emergency data signals are transmitted from any of the terminal units in a time interval during an AC power supply frequency cycle after the transmission of a polling signal and the terminal units engage in a contention for the transmission of the emergency data signals through the power supply line, the emergency data signals being received in the central processing unit during that time interval.