A motorized window treatment (110; 710; 1010; 1510; 1610) comprising: a covering material for a window moveable between a fully-open and a fully-closed position and any position intermediate the fully-open and fully-closed positions: a drive shaft; a motor drive unit (120; 720; 1020) having a motor coupled to the drive shaft such that the motor drive unit (120; 720; 1020) is operable to raise and lower the covering material by rotating the drive shaft, the motor drive unit having a sensor arrangement coupled to the drive shaft for sensing movement of the drive shaft and used for determining the position of a bottom of the covering material, the motor drive unit (120; 720; 1020) having a control unit coupled to the sensor arrangement for determining from at least one sensor signal from the sensor arrangement the position of the bottom of the covering material between the fully-open and fully-closed positions; wherein the covering material may be engaged by a user to manually position the covering material at any position between the fully-open and fully-closed positions and wherein the sensor arrangement provides said at least one sensor signal to the control unit so that the control unit can determine the position of the covering material when the covering material is manually adjusted; characterized by at least one lift cord rotatably received around the drive shaft and extending to the bottom of the covering material for raising and lowering the covering material; wherein the control unit further comprising a microprocessor having a sleep mode, the microprocessor using reduced electrical power during the sleep mode to conserve battery power; the motor producing an electromotive force when the window treatment (110; 710; 1010; 1510; 1610) is moved manually, the electromotive force being coupled to an input of the control unit to cause the microprocessor to change from the sleep mode to an active mode, whereby the control unit receives and processes the sensor signal to determine the position of the covering material when the covering material is manually adjusted. a covering material for a window moveable between a fully-open and a fully-closed position and any position intermediate the fully-open and fully-closed positions: a drive shaft; a motor drive unit (120; 720; 1020) having a motor coupled to the drive shaft such that the motor drive unit (120; 720; 1020) is operable to raise and lower the covering material by rotating the drive shaft, the motor drive unit having a sensor arrangement coupled to the drive shaft for sensing movement of the drive shaft and used for determining the position of a bottom of the covering material, the motor drive unit (120; 720; 1020) having a control unit coupled to the sensor arrangement for determining from at least one sensor signal from the sensor arrangement the position of the bottom of the covering material between the fully-open and fully-closed positions; wherein the covering material may be engaged by a user to manually position the covering material at any position between the fully-open and fully-closed positions and wherein the sensor arrangement provides said at least one sensor signal to the control unit so that the control unit can determine the position of the covering material when the covering material is manually adjusted; characterized by a drive shaft; a motor drive unit (120; 720; 1020) having a motor coupled to the drive shaft such that the motor drive unit (120; 720; 1020) is operable to raise and lower the covering material by rotating the drive shaft, the motor drive unit having a sensor arrangement coupled to the drive shaft for sensing movement of the drive shaft and used for determining the position of a bottom of the covering material, the motor drive unit (120; 720; 1020) having a control unit coupled to the sensor arrangement for determining from at least one sensor signal from the sensor arrangement the position of the bottom of the covering material between the fully-open and fully-closed positions; wherein the covering material may be engaged by a user to manually position the covering material at any position between the fully-open and fully-closed positions and wherein the sensor arrangement provides said at least one sensor signal to the control unit so that the control unit can determine the position of the covering material when the covering material is manually adjusted; characterized by