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. The transmission of a modulated second signal may be disabled when the received first electromagnetic EHF signal indicates that the first and second shield portions are not in alignment.