Power window

Power assists originated in the need and desire to move convertible body-style tops up and down by some means other than human effort.

The earliest power assists were vacuum-operated and were offered on Chrysler Corporation vehicles, particularly the low-cost Plymouth convertibles in the late 1930s.

Shortly before World War II, General Motors developed a central hydraulic pump for working convertible tops.

Previously, GM had used a vacuum system which did not have the power to handle increasingly larger and complex (four side-windows vs. only two) convertible top mechanisms.

[5] These systems were based on major hydraulic advances made in military weapons in preparation for World War II.

The "Hydro-Electric" system (windows, front seat adjustment and convertible top) was standard on 1947 model year.

Modern heavy-duty highway tractors frequently have an option for power window controls; however, these are generally what is referred to as "straight air".

However, some models like Saab, Volvo, Mazda and Holden have used switches located in the center console, where they are accessible to all the occupants.

This also removes the need to produce separate door components and wiring for left and right-hand drive variants.

It would be a simple thing to allow electric power windows to be operable when the ignition is turned off, however it would also make the car much easier to steal.

Many modern cars have a time delay feature, first introduced by Cadillac in the 1980s, called "retained accessory power".

[13] However, the rules do not prevent all potential injuries to a hand, finger, or even a child's head, if someone deliberately holds the switch when the window is closing.

In 2009, the U.S. auto safety administration tentatively decided against requiring all cars to have automatic reversing power windows if they sense an obstruction while closing.