A drop deck trailer frame includes a front section having a first upper surface, a rear section having a second upper surface lower than the first upper surface, and an improved connection between the front and rear sections which tends to reduce cracking which commonly occurs in drop deck trailer frames due to the stresses in the region of the connection. The swinging arm has a plurality of holders and a lock mechanism that removably engages the swinging arm with a portion of the wire frame base. The method includes using a high nickel alloy for both of the signal wire and the ground wire to manufacture a sensor in the first air-voltage range, and using a high nickel alloy for only one of the signal wire and the ground wire to manufacture a sensor in the second air-voltage range.