CSMIO/IP-M - wiring sanity check needed

[Washout]

Hi all,

I'm currently rebuilding my old CNC controller with a shiny "new" enclosure and using the CSMIO/IP-M as the core (with MACH4 replacing MACH3).

From diagrams in the manual/cs-labs web site, as well as JAZZCNC's diagrams in other threads, I see that for e-stop and sensors the circuit for those takes both a 24v +ve from the PSU through the e-stop switch to a (+) input and then the other side takes a -ve from the PSU to the corresponding (-) input i.e. pins 1 and 14 for pair 0.

Question is, on my previous controller board there was just a plain circuit for the e-stop with 5v and 0v terminals and the e-stop switch in between, so why does the PSU feed need to be in the circuit for the e-stop on the CSMIO/IP-M, given that the PSU is powering the controller in the first place via its power connector?

Same goes for a ruby tipped probe or z height plate circuit, which I will also need to wire in a similar manner if I am reading the literature correctly.

Just checking before the first power up this week(end) and hopefully avoid any magic smoke if I have misinterpreted something.

Also if I decided to go with a 4PDT relay option, which version out of the options in the link below, would I need (I'm currently assuming the 220V AC one if I'm using it to cut the feed to the stepper's transformer)?

https://www.amazon.co.uk/dp/B07JNBSP..._g3pPDbJR2YXFQ