A surface-plasmon electric field sensor has a plasmonic portion having an electro-optic dielectric material coated on one side with a transparent conductive layer and on another side with a thin layer of conductive metallic layer. Fingertip caps are connected to finger tension leads that extend rearwardly to connect to a finger tensioner attached to the forearm support. Moreover, the assisting device passively waits to rendezvous with the joining device remotely through its network interface. The method also includes applying a beamforming steering matrix to the second preamble portion of the first data unit but not to the first preamble portion of the first data unit. The primary seal element includes a first surface cooperating with a second surface of the seal runner to form a circumferential seal between the primary seal element and the seal runner. A plurality of spring members are respectively sleeved on and bias the fastening elements to move away from the base plate.