SPDT switch cable

Can the C and NC of a SPDT( 24vdc) switch be wired in 2 core cable or would it need to be a 3 core cable with one cable for earth ?

Thank you
FMR62 is a high spec Radar sensor designed for SIL3 applications - and your query relates to a 2wire volt free contact cable / cores / earthing ?

If it were any other sensor I would suggest 2 cores or 2 core cable. If you have an earthing diagram I would show bonding to the sensor case although many installations bond without prompting.

If this FMR62 is part of a SIL3 design, I would expect the cable be subject to a HAZOP / Safety Design Study, as it’s
Physical, environmental and routing properties would be subject to close scrutiny; and an earthing study with supporting calculations to show what earthing is needed and why.