Yup, there is a control wire for the magnetic coil.
i have a 2004 BMW X5, the year BMW switched the AC compressor from a standard Denso to a variable displacement Calsonic. Those variable displacement Calsonics had pulley clutches as early as back then.
I didnt know it back then, and it got me scratching my head losing AC intermitently but seeing the compressor clutch engaged, till I learned it was a variable displacement compressor lol!