DS-3578 scanner RS 232

We have some DS-3578 scanners connected to cradles, which again are connected to a USB port on the computer.

My challenge is that I need to split the signal, on other scanners I do that by running a RS 232 cable from the cradle, to a “home made” split cable, that again goes to 2 Prolific Serial to USB converters.Giving me the same signal on two different COM ports.

But when I try to set the DS-3578 in RS 232 mode I don’t get any signal at all, does anyone know how to do this properly?