Abstract: A door opening system includes a power transmission mechanism, a trolley, and a connecting arm. The power transmission mechanism includes a motor, a drive wheel driven rotatably by the motor, an indirect wheel, and a tension wheel. A transmission rope is trained on the drive, indirect and tension wheels in a closed loop such that parts of the transmission rope extend along a spiral path on the drive and indirect wheels, and do not contact each other, and such that rotation of the drive wheel drives the indirect and tension wheels rotatably. The trolley is coupled to the transmission rope, and is disposed between the indirect and tension wheels of the power transmission mechanism. The connecting arm has a first end coupled to the trolley, and a second end adapted to be coupled to the garage door.

Abstract: A communications system includes a transmitting device for processing packets to be sent, and a receiving device for processing the transmitted packets. The transmitting device includes a first memory unit, a first communications unit, and a first processing unit coupled therebetween. The first processing unit is operable so as to compose an initial packet segment, encrypt the initial packet segment, form a transmit packet, and enable the first communications unit to transmit the transmit packet. The receiving device includes a second communications unit, a second memory unit, and a second processing unit coupled therebetween. The second processing unit is operable so as to determine if there is any error in the transmit packet, decrypt the encrypted packet segment of the transmit packet, verify the transmit packet, and process the data transmitted in the transmit packet.