the drive p fet 40 is enabled during printing whenever the u2018 row enable u2019 re 98 and u2018 column enable u2019 ce 100 are both asserted receive u2018 1 u2019 s at their contacts enabling the drive fet 40 opens the heater element 34 to vpos 104 to activate the unit cell when the row enable 98 or the column enable 100 are not asserted the bleed n fet is enabled the bleed n fet 112 ensures that the voltage at the sense node 120 is pulled low when the unit cell is not activated to eliminate any electrolysis path when the oat 106 is asserted the and gate 108 pulls the gate of the drive p fet 40 high to disable it asserting the oat 106 also pulls the gate of the sense n fet 114 high to connect the sense output 116 to the sense node 120 with the bleed n fet 112 disabled the voltage at the sense node 120 will still be pulled low through the heater element 34 to ground 68 accordingly the sense output 116 is low to indicate that the actuator is still operational however if the heater element 34 is open failed the voltage at the sense node 120 remains high and this pulls the sense output 116 high to indicate a dead nozzle this is fed back to the pec which updates the dead nozzle map and initiates measures to compensate if possible the unit cell circuitry shown in fig1 b uses.