@ Silyavski, thank you very much for taking the time to go thru my VFD manual to help me. I think I'll get it going now and I will also connect the VFD failure relay to my EStop circuit.

@Neale, Ahh, thx, now that makes a lot more sense to me. I can now see why one would use this. I guess emulating the functionality by using a few relays that drop out on estop would not be impossible but getting the reset functionality to work would be very difficult for me, so it would be a lot easier to just use a component. Had a look on RS-online but new they are expensive so I'll try and find a second hand or discontinued one from a seller thas will to send here. Just wondered why on earth they call some models a PNOZ, do they know what it sounds like when you pronounce it in english :-)

@Eddy, thanks that's a very useful link.

BTW you guys were right, I did a cad layout of my control box this weekend and its MUCH larger than I thought if I follow the component manufacture's guidelines for spacing between parts. I'm going to need a small lotto win to complete this machine if I want a nice PNOZ, a steel enclosure and a CSMIO/IP-M. Scratching around to see if I can't maybe liquidate some other redundant hobby stuff :-)