This disclosure is directed to techniques for estimating signal-to-noise ratio of signals received by a wireless communication device. The first-type connector and the second-type connector are exposed through a surface of the package component. Throughout late stance, joint impedance is minimized so as not to impede powered plantar flexion movements, and during the swing phase, a torsional spring-damper control lifts the foot to provide toe clearance. The first and second layers are removed from over the block while leaving portions of the first and second layers over the region proximate the block. The magnet plug and magnetic switch plug have countersink heads to seat in the hinge fastening holes and insert through juxtaposed hinge holes into drilled holes in the door and wall jambs. The second lens group is moved to the object side along an optical axis thereof to perform a variable power operation from a wide angle end to a telephoto end of the variable power optical system, and the first lens group is moved to make a correction of an image plane position in accordance with the variable power operation.