This part is a kind of semiconductor called 20PMT04B.

Function of this product has (20PMT04B / 20PMT05B) Single 10Base-T/100Base-TX Transformer Design.

Manufacturers : YCL

Image and pinout :

Some of the text within the PDF file :

YCL Single 10Base-T/100Base-TX Transformer Design for varied turn ratio on Tx side ♦Designed to meet IEEE802.3u requirement. ♦Primary inductance 350µH min. with 8mA DC Bias ♦PTH Type Electrical Characteristic @25° C Insertion Loss Return Loss Turn Ratio Model No. dB Typ dB TX/RX 0.1-100MHz 30/60/80MHz PH163003B 1:1/1:1 1.0 -16/note/-10 20PMT04B 1:1/1:1 1.0 -16/note/-10 20PMT05B 1:1/1:1 1.0 -16/note/-10 PT163031B 2:1/1:1 1.0 -16/note/-10 Note : Greater than 16-20log(f/30MHz) Cross Talk Schematic dB Typ 60/100MHz -40/-38 S-1 -40/-38 S-3 -40/-38 S-2 -40/-38 S-4 Dimension Date : Jan.03,2000 YCL Schematic S-1 1 Single 10Base-T/100Base-TX Transformer Design for varied turn ratio on Tx side S-2 16 15 3 4 5 6 13 TX 2 3 4 15 RX 16 14 13 1 8 6 7 12 10 9 10 11 9 [ ... ]

20PMT04B PDF Datasheet Download