The XPSASF is quite an ancient model that was initially replaced by the XPSAK.
For a comparison between them please check please check the attached file "XPSASF to XPSAK.pdf"

The XPSAK is now obsolete as well and was replaced by XPSUAK.
For a comparison between them please check please check the attached file "XPSAK to XPSUAK.pdf"

Although most applications will allow the use the XPSUAK with minor wiring changes there might be situations where the application will have to be changed/adapted to incorporate the new safety relay.