| connector end Pin | Pin Name |
Description |
| 9 | phototransistor cathode | green wire |
| 5 | phototransistor anode | white wire; phototransistor detects level of IR and/or red light transmitted through the finger |
| 7 | shield | cable shield, connects to copper shield over the phototransistor |
| 2 | LED1 | red wire; anode of the IR LED, cathode of the red LED |
| 3 | LED2 | black wire; cathode of the IR LED, anode of the red LED |
Across pins 2 and 3, I see different voltage drops depending on polarity; so I think the single 2-pin package connected to those pins is actually both IR and red LEDs together, and the instrument would probably apply first one polarity, then the other, to alternately measure conductance of IR and red light through the patients finger.
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