External rear view mirrors have been provided on trucks and similar vehicles for a great many years.  Such mirrors are a familiar sight generally comprising a pair of elongated vertically oriented mirrors on each side of the vehicle cab and supported by a pair of support structures often having a number of bracing elements.  These mirrors are generally utilized to provide driver vision along each side of the vehicle and for a vision angle extending outwardly from the vehicle.  Because different drivers having different height and seating positions require correspondingly different mirror positions to properly utilize such mirrors, an adjustable support is used in coupling each mirror to its respective support structure.  The process of manually adjusting such mirrors is difficult and often tedious.  The passenger side mirror in particular requires repeated attempts on the driver's part to adjust the mirror and return to the driver's seat to determine proper mirror adjustment.  Generally, several such cycles are required before the mirrors are finally adjusted to suit a particular driver.  Of course, the next driver operating the vehicle then carries forward an adjustment process which is no longer suited to the original driver.  The end result is a tiresome process for each driver upon assuming operating control of the vehicle. 
In many "backing" and "cornering" maneuvers, the trailer moves out of the field of view making the standard, unpowered mirror useless of observing the rear of the trailer. 
The difficulties and effort required by drivers in adjusting such vehicle mirrors has prompted practitioners in the art to provide power adjustable mirrors for trucks and similar vehicles.  The basic function of such powered mirrors is similar to that provided for automobiles and the like in that a drive motor such as a two direction DC motor is coupled to the mirror through an operative mechanism and to a driver accessible control unit.  The intent is to provide mirror movement in response to operator control and avoid the need for repeatedly moving about the truck cab and its exterior in order to properly adjust the vehicle mirrors. 
While the basic idea of power adjustable mirrors is of great promise and highly desirable to operators of trucks and similar vehicles, the presently available units provided by practitioners in the art are subject to several significant problems and limitations.  For example, the drive mechanisms used to operate such mirrors have, to date, often proven to be rough or uneven in their motion response which renders adjustment erratic and difficult.  In addition, such powered mirrors are often subject to irritating overshoot characteristics in which the drive mechanism "runs on" in a given direction for a brief interval once the control is released.  The renders adjustment somewhat vexing and requires repeated driver involvement.  In addition to adjustment problems, the presently available powered mirrors for trucks and similar vehicles are often subject to mirror movement or severe damage when an impact is imparted to the mirror from objects such as tree branches, persons walking to close to the vehicle or other inadvertent contact with the mirror.  In addition, the durability and reliability of presently available mirrors for trucks or similar vehicles is far less than desired causing such mirrors to become a source of frequent repair problems. 
The limited utility of existing powered mirrors combined with their high cost has kept the unpowered, manually adjustable mirror in the great majority of use.  The need for greater vehicle safety has created the limited existing market for powered mirrors. 
There remains, therefore, a need in the art for evermore improved powered vehicle mirrors of the type suitable for use on trucks and other vehicles.