The Duodrivetrain™ - and its sister product, Monodrivetrain™ - are conceived to be units which are returned to the nearest Duodrive facility. They are highly standardised and it is envisaged that an exchange unit, if not kept on site by an operator, would normally be available on a next day basis following receipt of the unit which was requiring service and where the user has already entered into a Service Support Contract with Duodrive Limited.