Does the Ethernet port uses and RJ-45socket to connect a laptop to a standard telephone line?
RJ45 was designed for LAN connection only. For modem lines you need RJ11. Thus the answer is NO.
Maybe the ethernet cable is not your problem. Ethernet cables are available everywhere and they all should work for the PS3, PC, router, modem, etc. ethernet ports are one way and are either in or out. The spot on back of the PS3 to connect an ethernet is a standard size and is meant to connect to a modem or a router or it will not work.
You can use a switch to connect different pieces of equipment. For example, a standard ADSL router only has a port for a single Ethernet cable. If you want to connect 2 or more computers to the Internet, you can use a switch. In this case, the ADSL router and each computer connect to the switch, via a standard Ethernet cable. If you don't have an Internet connection, you can still set up a home…