300’s were originally hard wired, flat metal connection box with a strip of connector block on it, the later models had infra red remotes with the receiver box mounted under the rail next to the trailing cable box as in your picture, a link cable connected the two boxes and carried the signals
as you dont seem to have that? I would lean towards yours being a 400 with the i/r receivers being mounted in the carriage, a picture of the carriage would help? or metal square edge carriage = 300, curved plastic carriage covers with trailing cable= 400, plastic covers no trailing cable= 420 or overseas markets 310, 410…..
Let us know what model it is, and chair type and I’ll possibly be able to dig out a drawing and possibly a full remote set up with cables, think i have a set stashed away in my spares box in the garage
