2013 WPX Contest rules now available in 10 languages. Summary of rule changes in new blog entry. http://www.cqwpx.com/blog/?p=112
CQ WPX Contest Blog » Blog Archive » WPX Rules for 2013
IV(h) - New rule that requires stations using more than one transmitter on a band to have a mechanical lockout in order to prevent more than one transmitted signal at a time.