A:
Ah you mean MYAXIS POINT. Yes but why? Only reason would be that you that they both expect to connect to an intermediate device. You might be better off with what is called a 'cross over cable' with that you can connect two computers directly together. Or your modem and you point of sale device. If you can't get a cross over cable then the switch will work.
Background:
Yes but you could NORMALLY connect only one device. Your modem may have a built in router (my old DSL modem did). The function of home routers is to take a single IP address that the world knows about and map that to multiple IP addresses, usually beginning with '192.168.1.' (also known as Network Address Translation). If your connection to the Internet expects to see multiple IP addresses on the side connected to the switch then you don't need a LOCAL router, there is a router external to the modem, but I've never seen that in a home situation. At work we have 128 IP addresses passed to us but that is a commercial connection. My cable modem at home just send over one. The switch just knows about IP addresses that connect to each of its ports, it doesn't know who assigned them.