Patent ID: 7932480

Claim:
Heater control apparatus, comprising: A. A plurality of heater controllers, each of which comprises a signal relay switch with an open circuit mode and a closed circuit mode, and each of which comprises a process control circuit that is programmed to: (i) compare preset temperature range parameters that represent a predetermined desired operating temperature range to temperature information from a heater to determine whether the temperature information from the heater is within the desired operating temperature range; (ii) cause the signal relay switch to close when the temperature information is within the desired operating temperature range; and (iii) cause the signal relay switch to open when the temperature information is not within the desired temperature range; and B. A remote temperature monitor system comprising: (i) a remote signal power supply connected electrically to a signal circuit that connects the signal relay switches in all of said heater controllers in series, whereby the signal circuit is closed by all of said signal relay switches in all of the heater controllers being closed and whereby the signal circuit is opened by at least one of said signal relay switches being open; (ii) a continuity detector attached electrically to the signal circuit, said continuity detector being capable of detecting whether the signal circuit is an open circuit or a closed circuit; and (iii) a signal generator that is responsive to the continuity detector to generate an alert/alarm signal, which is indicative of the temperature information from the heater being outside of the desired operating temperature range, whenever the continuity detector detects that the signal circuit is open.