leads 51 53 connected to calibration element 56 one value is provided to a look up table 62 to determine appropriate wavelength dependent coefficients for the oxygen saturation calculation as in the prior art the other value s are then provided to another look up table s 63 which provides input e g coefficients to other calculations performed by controller 64 these additional calculations may enhance the performance and or safety of the system controller 64 provides signals to a drive circuit 66 to control the amount of drive current provided to leds 52 as in the prior art detector 54 is connected through an amplifier 72 and a filter 74 to an a d converter 76 this forms a feedback path used by controller 64 to adjust the drive current to optimize the intensity range of the signal received for proper operation the signal must be within the analog range of the circuits employed the signal should also be well within the range of a d converter 76 for example one rule that may be applied is to adjust led drives and amplifier gains so that both red and ir signals fall between 40 and 80 of full scale reading of converter 76 this requires correct and independent settings for both the red and infrared leds in an embodiment of the present invention patient specific data such as trending data or patient monitoring parameters can be actively stored in the memory of memory chip 56 as the patient and sensor travel from ward to ward of the hospital and consequently plug into different oximeters the patient specific data can be read from memory 56 of.