This post describes for the transformer.
The part number is HST-2027DR.
The function of this device is 10/100BASE-TX transformer module.
The manufacturer of this part is GROUP-TEK (www.group-tek.com).
See the preview image and the PDF file for more information.
This is 10/100 Base-TX Transformer Module for Auto MDI / MDIX Applications.
1. Designed to meet IEEE 802.3 requirements
2. Designed for multiport repeater & ethernet switching hub application
3. Environmental Designed to meet IR 250 degree C for 1minute
4. Primary inductance (LP):350uH,min.@100KHz 0.1Vrms 8mA