DECA is a hub, not a switch. It has few, if any of the features that distinguish a switch from a hub. It is the switch that you plug your Broadband DECA into that lends its switch-like functionality to DECA.
Exactly how does plugging DECA into a router cause DECA to suddenly have switch-like characteristics when (according to you) it didn't have these characteristics prior to being plugged into the router? DECA doesn't magically become something else just because you've connected an Ethernet cable to a router.