This part is a kind of semiconductor called AMC127.

Function of this product has Opto-Coupler.

Manufacturers : Alpha Micro Components

Image and pinout :

Some of the text within the PDF file :

AMACM12C7127 Surface Mount High Voltage Opto-Coupler PRELIMINARY INFORMATION AMC 127 Opto-Coupler FEATURES • High Vceo (300Volts) • UL approval E196140 • High Current Transfer Ratio (1000 min @ 1mA) • High Isolation Voltage between LED and Opto Transistor (3750Volts) • Mini-flat Surface mount Package 4-pin Mini-Flat Package AMC 127 xxx GENERAL DESCRIPTION The AMC127 High Voltage Opto Coupler may be used in a variety of applications where high isolation is required between primary and secondary circuits, in addition to high current transfer ratio between these circuits. The Opto-Transistor side of the AMC127 is capable of withstanding Voltages of up to 300 Volts without sustaining damage to the device. Designed for use in telecommunications and data communications equipment [ ... ]

AMC127 PDF Datasheet Download