This part is a kind of semiconductor called BY127.

Function of this product has GENERAL PURPOSE PLASTIC RECTIFIER.

Manufacturers : Shanghai Lunsure Electronic Tech

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Some of the text within the PDF file :

CE CHENYI ELECTRONICS BY127,BY133,EM513,EM516 GENERAL PURPOSE PLASTIC RECTIFIER Reverse Voltage - 1250 to 1800 Volts Forward Current - 1.0Ampere FEATURES . The plastic package carries Underwrites Laboratory Flammability Classification 94V-0 . Construction utilizes void-free molded plastic technique . Low reverse leakage . Low forward voltage drop . High forward surge current capability . High current capability . High reliability MECHANICAL DATA . Case: JEDEC DO-41 molded plastic body . Terminals: lead solderable per MIL-STD-750,method 2026 . Polarity: Color band denotes cathode end . Mounting Position: Any . Weight: 0.012 ounce, 0.33 gram MAXIMUM RATINGS AND ELECTRICAL CHARACTERISTICS (Ratings at 25 ambient temperature unless otherwise specified,Single phase,half wave 60Hz,resistive o [ ... ]

BY127 PDF Datasheet Download