as illustrated in fig3 to 5 , the present invention generally comprises a circuit board 12 , a motor 3 , a lifting rack 17 and other components . the motor 3 is a low voltage direct current motor which drives the lifting rack 17 to move upwards or downwards through a set of gears , a set of clutch gears and a driving gear bar 19 . on the circuit board 12 , a transformer 13 is installed to reduce the voltage of the alternating current to supply 6v power , and power is supplied to the circuit board 12 and the motor 3 through a set of diode rectifiers changing the alternating current to direct current . the set of gears comprises an endless screw 4 which connects and rotates with the motor 3 , and two or more straight - tooth gears 5 which are intermeshed with one another and mesh and rotate with the motor 3 . one side of the straight - tooth gears 5 meshes with one side of the set of clutch gears . the set of clutch gears comprises a transmission shaft 10 and a clutch straight - tooth gear 11 , a clutch spring 9 and two or more intermeshed clutch gears 7 , 8 which are installed the transmission shaft 10 . one side of the clutch gears 7 meshes with the straight - tooth gear 5 . one side of the clutch straight - tooth gear 11 meshes with the driving gear bar 19 . when the motor 3 rotates , the set of gears drives one clutch gear 7 in the set of clutch gears to rotate . the rotating clutch gear 7 is pushed by the tension which is created by the clutch spring 9 towards the second clutch gear 8 and drives it to rotate . the second clutch gear 8 drives the clutch straight - tooth gear 11 to rotate through the transmission shaft 10 . the clutch straight - tooth gear 11 drives the driving gear bar 19 to move upwards or downwards . one side of the lifting rack 17 connects to a holder placed inside the toaster slots and the other side is connected to the driving gear bar 19 . the upward or downward movements of the driving gear bar 19 drive the lifting rack 17 to move upwards or downwards accordingly . the lifting rack 17 drives the slices of bread on the holder to move upwards or downwards accordingly . when the lifting rack 17 is out of order and becomes immovable , the driving gear bar 19 cannot move upwards or downwards and so the clutch straight - tooth gear 11 and the second clutch gear 8 cannot rotate smoothly . when the first clutch gear 7 is driven to rotate by the motor 3 and the set of gears , the first clutch gear 7 compresses the clutch spring 9 and moves away from the second clutch gear 8 . the first clutch gear 7 and the second clutch gear 8 skid at the point of contact , thus releasing the driving force generated by the rotation of the motor 3 . the lifting rack 17 has a latch 18 disposed in a position corresponding to the upper sensor 15 and the lower sensor 16 . when the lifting rack 17 ascends to a horizontal position corresponding to that of the upper sensor 15 , the latch 18 contacts the upper sensor 15 and the upper sensor 15 immediately sends electrical signals to the circuit board 12 . the preset programs of the integrated circuit of the circuit board 12 control the motor 3 to stop rotating . the lifting rack 17 is then stopped from ascending continuously . when the lifting rack 17 descends to a horizontal position corresponding to that of the lower sensor 16 , the latch 18 contacts the lower sensor 16 and the lower sensor 16 then immediately sends electrical signals to the circuit board 12 . the preset programs of the integrated circuit of the circuit board 12 control the motor 3 to stop rotating . the lifting rack 17 is then stopped from descending continuously . the integrated circuit of the circuit board 12 contains custom software to preset timing for the programs . it automatically cuts off the power supply to the motor 3 after the expiration of the preset time limit of 10 seconds , so as to stop the motor 3 from rotating continuously , thus preventing the motor 3 or other components from malfunctioning . the power supply of the heating wire uses a relay 14 as a switch . the relay 14 is electrically connected to the power source , the circuit board 12 and the heating wire respectively , and is operated and controlled by the preset programs of the integrated circuit of the circuit board 12 . upon completion of the preset programs , the power supply to the relay 14 is automatically cut off and the relay 14 immediately cuts off the power supply to the heating wire . when the descending procedure of the lifting rack 17 functions improperly , the lower sensor 16 does not send any electrical signal to the circuit board 12 , and the circuit board 12 does not supply power to the relay 14 and so the relay 14 does not switch on the heating wire . therefore , malfunctions of the lifting rack 17 or the motor 3 can be avoided . it can also prevent a slice of bread from getting stuck inside the slot and being immovable , thus reducing the possibility of causing a fire . the circuit board 12 contains a set of specially designed circuits which controls in a manner that when any fault , abnormality or overheating occurs in the timing or circuit programs of the circuit board 12 , the circuit board 12 sends instructions to cut off the power supply to the heating wire , preventing power from being continuously supplied to the toaster , thus causing fires . the motor 3 , the set of gears and the set of clutch gears are disposed inside a substantially enclosed casing 1 , 2 . the casing 1 , 2 is placed on one side of the circuit board 12 . the casing 1 , 2 encloses the noise generated by the rotation of the motor 3 , the set of gears and the set of clutch gears , thus having the function of reducing the noise . lubricants can be added to the set of gears , the set of clutch gears and the driving gear bar 19 to reduce the frictions among the gears while rotating , thus having the function of reducing the noise and tear and wear of the gears . to use the toaster , the user inserts the plug to a power socket . power is supplied to the circuit board 12 through a transformer 13 to reduce the voltage and a set of diode rectifiers to change alternating current to direct current . the user places a slice of bread into the holder in the slot and switch on the toaster . the circuit board 12 receives instructions and sends a “ descending signal ” of a preset time limit of 10 seconds to the motor 3 . the motor 3 then starts to rotate in one direction and drive the endless screw 4 to rotate . the endless screw 4 drives the straight - tooth gears 5 to rotate . the straight - tooth gears 5 drive the set of clutch gears to rotate . the set of clutch gears drives the driving gear bar 19 to move downwards through the clutch straight - tooth gear 11 . the downward movement of the driving gear bar 19 drives the lifting rack 17 and the holder to move downwards until the lower sensor 16 senses the latch 18 of the lifting rack 17 . the lower sensor 16 then sends a “ descending completed signal ” to the circuit board 12 immediately . the circuit board 12 cuts off the power supply to the motor 3 , and the motor 3 stops rotating and the lifting rack 17 stops descending . the circuit board 12 then sends a “ start - to - toast signal ”. the whole process takes about 3 seconds . if the circuit board 12 does not receive any signal from the lower sensor 16 within the preset time limit of 10 seconds , the circuit board 12 will automatically cut off the power supply to the motor 3 and will not send any “ start - to - toast signal ”. when the circuit board 12 sends a “ start - to - toast signal ”, the relay 14 is instructed to supply power to the heating wire to heating up and then to toast the slice of bread and at this point of time , the circuit board 12 starts to count the time . upon expiration of the preset time , the circuit board 12 sends a “ toasting completed signal ” and cuts off the power supply to the relay 14 and the relay 14 immediately cuts off the power supply to the heating wire , thus preventing the heating wire from heating continuously . the circuit board 12 then sends an “ ascending signal ” of a preset time limit of 10 seconds immediately . the motor 3 starts to rotate in reverse direction and drives the endless screw 4 to rotate in reverse direction . the endless screw 4 then drives the straight - tooth gears 5 to rotate in reverse direction . the straight - tooth gears 5 drive the set of clutch gears to rotate in reverse direction . the set of clutch gears drives the driving gear bar 19 to move upwards through the clutch straight - tooth gear 11 . the upward movement of the driving gear bar 19 drives the lifting rack 17 and the holder to move upwards until the upper sensor 15 senses the latch 18 of the lifting rack 17 . the upper sensor 15 then immediately sends an “ ascending completed signal ” to the circuit board 12 . the circuit board 12 then cuts off the power supply to the motor 3 , and the motor 3 stops rotating and the lifting rack 17 stops ascending . if the circuit board 12 does not receive any signal from the upper sensor 15 within the preset time limit of 10 seconds , the circuit board 12 will automatically cut off the power supply to the motor 3 .