My current understanding of the physical layer is:
I was told that when a network interface card (NIC) wants to send signal onto wire, it will low its voltage. And thus the signal will be imposed onto the wire.
NIC 1 lowers its voltage, and thus some electric potential difference will occur between itself and other NICs, and thus electric current will be intrigued. By detecting this current, signal can be detected.
But my question is:
If there are many other NICs connected to a shared wire, will the electric current be weakened?
Or do all the NICs only talks directly to a central device?
(Such that a central device like a router, switcher or a hub is responsible to propagate the signal widely)
Could someone give some elaboration?