This part is a kind of semiconductor called L51P3C.

Function of this product has Photo Transistor.

Manufacturers : Kingbright Electronic

Image and pinout :

Some of the text within the PDF file :

PHOTOTRANSISTOR L51P3C Features !MECHANICALLY AND SPECTRALLY MATCHED TO Description Made with NPN silicon phototransistor chips. THE L53 SERIES INFRARED EMITTING LED LAMP. !WATER CLEAR LENS. Package Dimensions Notes: 1. All dimensions are in millimeters (inches). 2. Tolerance is ±0.25(0.01") unless otherwise noted. 3. Lead spacing is measured where the lead emerge package. 4. Specifications are subject to change without notice. SPEC NO:CDA0546 APPROVED:J.LU REV NO: V.1 CHECKED: DATE:NOV/01/2001 DRAWN:X.Q.ZHENG PAGE: 1 OF 2 Absolute Maximum Rating at T)=25°C Par am et er Collector-to-Emitter Breakdown Voltage Emitter-to-Collector Breakdown Voltage Power Dissipation at (or below) 25°C Free Air Temperature Operating Temperature Range Storage Temperature Rang [ ... ]

L51P3C PDF Datasheet Download