This is simple cable testing tool for checking your cables (e.g. ethernet patch cables or house installation). Complete tester consists of two modules and tested cable. Master (left) module is on the left. It is connected to the power supply (battery or wall adapter). Slave (right) is passive and has only LEDs.
Ethernet PHY is required in every microcontroller application which uses ethernet interface. It consists of RJ45 connector, transformers and PHY controller, which is analog circuit – interface between transformers and ethernet controller in microcontroller.
Circuit is divided in two PCB to keep it simple and single-sided. It connects via 20 pads (2,54mm raster) in dual row. Ethernet cables are usually stiff. Dual-in-line style of this module provides better mechanical rigidity.