Steering wheel first button added to the steering wheel was a switch to activate the car's electric horn. Traditionally located on the steering wheel hub or center pad, the horn switch was sometimes placed on the spokes or activated via a decorative horn ring which obviated the necessity to move a hand away from the rim. Electrical connections are made via a slip ring. A further development, the Rim Blow steering wheel, integrated the horn switch into the steering wheel rim. In 1966, Ford offered the Highway Pilot Speed Control Option, with steering wheel pad mounted rocker switches, on its Thunderbird. Uniquely,
Bicycle wheel of center. "Vertical truing" refers to adjustments of local deviations (known as hop) of the radius, the distance from the rim to the center of the hub. "Dish" refers to the left-right centering of the plane of the rim between the lock nuts on the outside ends of the axle. This plane is itself determined as an average of local deviations in the lateral truing. For most rim-brake bicycles, the dish will be symmetrical on the front wheel. However, on the rear wheel, because most bicycles accommodate a rear sprocket (or group of them), the dishing will often be asymmetrical: