This part is a kind of semiconductor called BY228.

Function of this product has CLAMPER / DAMPER GLASS PASSIVATED RECTIFIER.

Manufacturers : General Semiconductor

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Some of the text within the PDF file :

BY228 SERIES CLAMPER / DAMPER GLASS PASSIVATED RECTIFIER Reverse Voltage - 1500 Volts * D Case Style G3 Forward Current - 2.5 Amperes FEATURES ♦ High temperature metallurgically bonded construction ♦ Glass passivated cavity-free junction ♦ 2.5 ampere operation at TA=50°C with no thermal runaway ♦ Typical IR less than 0.1µA ♦ Hermetically sealed package ♦ Capable of meeting environmental standards of MIL-S-19500 ♦ High temperature soldering guaranteed: 350°C/10 seconds, 0.375" (9.5mm) lead length, 5 lbs. (2.3kg) tension P A T E N T E 1.0 (25.4) MIN 0.250 (6.3) 0.170 (4.3) DIA. 0.300 (7.6) MAX. 0.052 (1.32) 0.048 (1.22) DIA. 1.0 (25.4) MIN MECHANICAL DATA Case: Solid glass body Terminals: Solder plated axial leads, solderable per MIL-STD-750, Method 2026 Polarity: [ ... ]

BY228 PDF Datasheet Download