IEC 60947-5-8:2020 specifies requirements for three-position enabling switches. These switches are used as components of enabling devices to provide signals that,
- when activated, allow machine operation to be initiated by a separate start control, and
- when de-activated,
-- initiate a stop function, and
-- prevent initiation of machine operation.
This second edition cancels and replaces the first edition published in 2006. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
- due to the increasing range of useful applications of three-position enabling switches, note of scope, operational characteristics and tests are reviewed;
- figures for example of devices incorporating enabling switch are added in Annex A;
- new Annex B for procedure to determine reliability data for the switch used in functional safety applications is added.