A cable supporting assembly, comprising: a connecting device including a pair of connecting members consisting of a first connecting member and a second connecting member; and a cable supporting member having a first end portion and a second end portion and being movably mounted on the connecting device; wherein the cable supporting assembly further comprises a first mechanism arranged at one of the connecting device and the cable supporting member; and a second mechanism arranged at the other of the connecting device and the cable supporting member; wherein the first mechanism and the second mechanism are connectable with each other to keep the cable supporting member at a predetermined position with respect to the connecting device; wherein when the first mechanism and the second mechanism are not connected with each other, the cable supporting member is operable to leave the predetermined position and is movable to a first position or a second position with respect to the connecting device; and wherein the two end portions (58, 60) of the cable supporting member are each rotatably connected to a corresponding one of the first connecting member and the second connecting member via a shaft (57a, 57b), so that the cable supporting member is movably mounted between the first connecting member and the second connecting member and can be rotated in a first direction with respect to the connecting device between the second position and the first position and can be rotated in a second direction with respect to the connecting device between the first position and the second position, wherein the first position and the second position are opposite positions, characterized in that each of the first connecting member and the second connecting member of the connecting device comprises at least one position-limiting projection projecting from the first and the second connecting member (48a, 48b) and which respective projection abuts against the respective outer edge of the end portion (58, 60) of the cable supporting member when the respective end portion (58, 60) reaches the first position or the second position and which prevents the cable supporting member from rotating from the first position to the second position in the first direction with respect to the connecting device or from the second position to the first position in the second direction with respect to the connecting device. a connecting device including a pair of connecting members consisting of a first connecting member and a second connecting member; and a cable supporting member having a first end portion and a second end portion and being movably mounted on the connecting device; wherein the cable supporting assembly further comprises a first mechanism arranged at one of the connecting device and the cable supporting member; and a second mechanism arranged at the other of the connecting device and the cable supporting member; wherein the first mechanism and the second mechanism are connectable with each other to keep the cable supporting member at a predetermined position with respect to the connecting device; wherein when the first mechanism and the second mechanism are not connected with each other, the cable supporting member is operable to leave the predetermined position and is movable to a first position or a second position with respect to the connecting device; and wherein the two end portions (58, 60) of the cable supporting member are each rotatably connected to a corresponding one of the first connecting member and the second connecting member via a shaft (57a, 57b), so that the cable supporting member is movably mounted between the first connecting member and the second connecting member and can be rotated in a first direction with respect to the connecting device between the second position and the first position and can be rotated in a second direction with respect to the connecting device between the first position and the second position, wherein the first position and the second position are opposite positions, characterized in that each of the first connecting member and the second connecting member of the connecting device comprises at least one position-limiting projection projecting from the first and the second connecting member (48a, 48b) and which respective projection abuts against the respective outer edge of the end portion (58, 60) of the cable supporting member when the respective end portion (58, 60) reaches the first position or the second position and which prevents the cable supporting member from rotating from the first position to the second position in the first direction with respect to the connecting device or from the second position to the first position in the second direction with respect to the connecting device.