Establishing a communication link may include transmitting by a first device an unmodulated first electromagnetic EHF signal and receiving by a second device the first electromagnetic EHF signal. The second device may determine whether the received first electromagnetic EHF signal indicates that a first shield portion and a second shield portion are in alignment. The transmission of a modulated second electromagnetic EHF signal may be enabled when the received first electromagnetic EHF signal indicates that both the shield portions are in alignment and may be disabled when the received first electromagnetic EHF signal indicates that the first and second shield portions are not in alignment.