I am a bit confused by your question, but I can attmpt to help. A modem is short for a "modulator demodulator". In you question, an ISP modem converts one signa

I am a bit confused by your question, but I can attmpt to help. A modem is short for a "modulator demodulator". In you question, an ISP modem converts one signal (DSL, cable, fiber, etc.) to another signal (ethernet). The Ethernet signal goes into a router, and the routers job is to make sense of where it goes. The ISP side is known as a WAN (Wide Area Network) and the internal network is the LAN (local Area network). The router keeps track of traffic to understand where to put it all. that traffic then goes to your computer.