alterra stratix fpga however other fpga 39 s microcontrollers cpus or logic devices may be used controller 116 contains embedded software which controls the operation of controller 116 controller 116 receives input from line 123 which is connected to output 125 of receiver 124 controller 116 contains an internal timer receiver 124 is a current sensor having output 125 and input 126 receiver 124 has terminals 126 and 127 terminal 127 is connected to external power supply 130 through wall socket plug 129 and terminal 126 is connected to power line 132 the voltage on output 125 is a function of the magnitude of the current passing through terminals 126 and 127 receiver 124 is an isolated hall effect sensor such as those offered by allegro microsystems inc alternative current sensors such as a simple resistor voltage divider may also be used an analog to digital converter may need to be placed between receiver 125 and controller 116 depending upon the type of receiver and controller used receivers based on technology other than current sensors may also be used as will be described in the following embodiments power line 132 connects to line 133 which passes out inlet port 106 and travels within tubing 105 to medical apparatus 110 line 132 and 133 contain multiple wires including at least a ground wire and a power wire in the following example medical apparatus 110 is an electrosurgical device.