the present invention relates to a signal coupling / decoupling arrangement for coupling / decoupling a signal onto / from an ac power line . the arrangement comprises : a carrier structure having a first and a second surface , a first conductive layer for a power line having a first winding arranged on said carrier structure ; a second conductive layer for signal line having a second winding arranged on said carrier structure ; apertures extending from said first surface to second surface ; and a first magnetic core part extending in said aperture and contacting a second magnetic core part , said magnetic core parts forming a substantially closed magnetic circuit .