Abstract: A robot arm comprises a first and a second link, the first link having a proximal end and a distal end and the second link having a proximal and a distal end. A fixed pulley, with circumferential surfaces concentric with the first pivot axis is mounted at the proximal end of the first link. A second-link pulley is fixed to the second link for rotation about the second pivot axis. An end effector pulley is fixed to the end effector for rotation about the third pivot axis. A first belt drive is also provided and includes one or more belts connected between the circumferential surfaces of the fixed pulley and the second link pulley so that ratation of the first link relative to the fixed pulley about the first pivot axis causes rotation of the second link about the second pivot axis relative to the first link. One or more idler pulleys is provided and is rotatably mounted to one or both of the links.