As per John except this may be a mechanical 'NVR' with no coil, ie a straightforward Emergency Stop Switch without no-volt protection. If so the terminal codes might mean:
11 = 'Switch 1 on side 1' – connects to 12 = 'Switch 1 on side 2'
21 = 'Switch 2 on side 1' – connects to 22 = 'Switch 2 on side 2'
31 = 'Switch 3 on side 1' – connects to 32 = 'Switch 3 on side 2'
But beware; I'm guessing! Your switch may be a combination of Normally Open and Normally Closed contacts. Or John is right and one pair is for a NVR coil. Any clues on the box like a website. (I've had a few things recently where the buyer is expected to know the documentation is all online.)
Pictures, type no, where it came from etc. might help . Do you have a multimeter?
Dave
PS – happened again – while I was delayed catching a goose and sharpening my quill, the question got answered!
Edited By SillyOldDuffer on 08/03/2018 13:10:49