Depending on the version of the push-button BCU – 1-gang rocker or 2-gang rocker – centre plates are used with and without indication lights. The “upper” or “lower” rockers can be controlled with the push-button with “neutral position”, while only the “lower” rocker can be pressed with the push-button with “switch position”. The push-button BCU can only function with an application program i.e. the push-button BCU consists of the device (hardware) and the application program (software).