In an Intrinsically Safe (IS) PoDL/PoE system, a PHY in power sourcing equipment (PSE) has its differential transmit terminals coupled across a primary winding of an isolation transformer. One secondary winding is coupled between a positive terminal of a DC voltage source and a first wire of a twisted wire pair. Another secondary winding is coupled between a negative terminal (e.g., ground) of the DC voltage source and a second wire of the twisted wire pair. The secondary windings provide differential data signals output from the PHY's transceiver to the wire pair, while the DC voltage from the DC voltage source is coupled to the wire pair via the two secondary windings. The DC power is applied to a remote power device having a PHY that communicates with the PSE PHY. Therefore, the secondary windings have the dual purpose of DC-coupling and magnetically coupling the differential data to/from the PHY.