Patent ID: 7635174

Claim:
A method for detecting a status of a heater circuit on a heater chip to be used with a print head, wherein the heater chip comprises a plurality of heater circuits, each of the plurality of heater circuits comprising a heater and a first power device wherein the first power device is configured to allow sufficient current to flow through the heater to cause ejection of ink when the first power device is on, each of the plurality of heater circuits further comprising: a second power device configured to allow current to flow through the heater, wherein the current is insufficient to cause ejection of ink when the first power device is off and the second power device is on; and a test output in electrical communication with each of the other of the plurality of the heater circuits; the method comprising: receiving at the heater chip addressing information for a selected heater circuit; if a signal indicating a test should be performed is received at the heater chip, switching off the first power device corresponding to the selected heater circuit, wherein the second power device corresponding to the selected heater circuit is on, and a signal is placed on the test output indicative of a state of the selected heater circuit and the second power device is configured to warm at least one of the heater, a substrate on which the heater is formed, and the ink.