HELI-R Phototransistor Kingbright HELI-R Phototransistor features an SMD (surface-mounted diode) LED designed with NPN silicon phototransistor chips. This phototransistor is mechanically and spectrally matched to the infrared-emitting LED lamp. The HELI-R phototransistor provides level 3 moisture sensitivity. This phototransistor has an operating temperature range of -40°C to 85°C. The HELI-R phototransistor is ideal for use in infrared applied systems, optoelectronic switches, photodetector control circuits, and sensor technology.