This part of IEC 60947 specifies requirements for three-position enabling switches.These switches are used as components of enabling devices described in 10.9 of IEC 60204-1 to provide signals that, a) when activated, allow machine operation to be initiated by a separate start control, and b) when de-activated, i) initiate a stop function, and ii) prevent initiation of machine operation. NOTE 1 The enabling control function is described in 9.2.6.3 of IEC 60204-1. NOTE 2 This standard does not deal with enabling devices. This standard does not apply to: − three-position enabling switches for non-electrical control circuits, for example hydraulic, pneumatic; − enabling switches without three-position mechanism; − emergency stop devices (see IEC 60947-5-5).