A first device module comprises a first coupling arrangement; the first coupling arrangement comprising a first inductive coil, a first magnetic core positioned within the first inductive coil to form a first electromagnet, and a first control unit electrically connected to the first inductive coil. The first control unit is configured to supply first DC current to the first inductive coil to generate a first magnetic field to attract a second device module comprising a second magnetic element and a second inductive coil by magnetic force, and first AC current to the first inductive coil to inductively transmit a first data or power signal from the first inductive coil to the second inductive coil.