BP Series Ethernet Transformers HALO Electronics Back-Plane (BP) Ethernet Transformers offer an enhanced and reliable alternative to capacitor-coupled backplane circuits. These ethernet transformers enable the Auto-MDIX and auto-negotiation features of both current-drive and voltage-drive PHYs. The BP ethernet transformers are ideal for applications with boards connected to the same backplane. These backplane transformers are tested and confirmed by leading silicon vendors such as Broadcom™ and Marvell™.