Heartbeat communications

摘要

A dual channel communications method including: (A) providing a control system with a central control station and a remote sensor for sensing a process status, the central control station and the remote sensor being connected by a power supply line and an output line; (B) impressing a non-periodic high-amplitude process status signal on the output line at the remote sensor so as to transfer status information about the process status to the central control station; (C) simultaneously impressing a periodic low-amplitude low-frequency diagnostic condition signal on the output line at the remote sensor so as to transfer diagnostic information about an operating condition of the remote sensor to the central control station; (D) monitoring the electrical state of the output line at the central control station to detect the level of the non-periodic high-amplitude process status signal so as to receive status information about the process status at the central control station; and (E) monitoring the electrical state of the output line at the central control station to detect the presence of the periodic low-amplitude low-frequency diagnostic condition signal so as to receive diagnostic information about the operating condition of i) the remote sensor, ii) said power supply line and iii) said output line at the central control station.