An actuating device for orthosis comprising: a housing ; a motor having a motor shaft ; a transmission disposed in the housing and operatively connected to the motor such that the motor provides power to the transmission, the transmission comprising: a first stage having a first sprocket , a second sprocket , and a first drive belt tensioned by the first sprocket and the second sprocket, wherein the first sprocket is attached to the motor shaft; a second stage having a third sprocket , a fourth sprocket , and a second drive belt tensioned by the third sprocket and the fourth sprocket, wherein the third sprocket is attached to the second sprocket of the first stage; a third stage having a fifth sprocket and a sixth sprocket , and a third drive belt tensioned by the fifth sprocket and the sixth sprocket, wherein the fifth sprocket is attached to the fourth sprocket of the second stage; a first shaft , wherein the second sprocket, the third sprocket, and the sixth sprocket are attached to the first shaft; and a second shaft , wherein the fourth sprocket and the fifth sprocket are attached to the second shaft; and an actuating arm operatively connected to the sixth sprocket of the third stage of the transmission such that the power provided to the transmission by the motor causes the actuating arm to provide an output torque. a housing ; a motor having a motor shaft ; a transmission disposed in the housing and operatively connected to the motor such that the motor provides power to the transmission, the transmission comprising: a first stage having a first sprocket , a second sprocket , and a first drive belt tensioned by the first sprocket and the second sprocket, wherein the first sprocket is attached to the motor shaft; a second stage having a third sprocket , a fourth sprocket , and a second drive belt tensioned by the third sprocket and the fourth sprocket, wherein the third sprocket is attached to the second sprocket of the first stage; a third stage having a fifth sprocket and a sixth sprocket , and a third drive belt tensioned by the fifth sprocket and the sixth sprocket, wherein the fifth sprocket is attached to the fourth sprocket of the second stage; a first shaft , wherein the second sprocket, the third sprocket, and the sixth sprocket are attached to the first shaft; and a second shaft , wherein the fourth sprocket and the fifth sprocket are attached to the second shaft; and a first stage having a first sprocket , a second sprocket , and a first drive belt tensioned by the first sprocket and the second sprocket, wherein the first sprocket is attached to the motor shaft; a second stage having a third sprocket , a fourth sprocket , and a second drive belt tensioned by the third sprocket and the fourth sprocket, wherein the third sprocket is attached to the second sprocket of the first stage; a third stage having a fifth sprocket and a sixth sprocket , and a third drive belt tensioned by the fifth sprocket and the sixth sprocket, wherein the fifth sprocket is attached to the fourth sprocket of the second stage; a first shaft , wherein the second sprocket, the third sprocket, and the sixth sprocket are attached to the first shaft; and a second shaft , wherein the fourth sprocket and the fifth sprocket are attached to the second shaft; and an actuating arm operatively connected to the sixth sprocket of the third stage of the transmission such that the power provided to the transmission by the motor causes the actuating arm to provide an output torque. <EOS>