A pulse oximeter sensor (30) includes a sensor plug (32), a cable (34), a light emitting unit (36), and a light receiving unit (38). The light emitting unit includes a first diode (50) and a second diode (52) mounted in an anti-parallel relationship between a first lead (60) and a second lead (62). The light emitting unit further includes a third light emitting diode (54) which is connected back-to-back between the second connector and a third connector (64) in a common anode relationship to the first diode and/or a fourth light emitting diode (56) connected across the second and third leads in an anti-parallel relationship with the third light emitting diode. An adapter cable (20) extends between the sensor plug (32) and a monitor (10) to adapt the sensor plug to a configuration of a socket (18) of the monitor.
