RJ 15
RJ-45 Ethernet, RJ-11 Modem
Ethernet cable is RJ 45. Dial-up modem is RJ 11
RJ11
RJ 11
DTEhttp://www.flashcardmachine.com/hardware.html~tekno
Depending on how old the modem is, it may connect to the serial port, the USB port, or an internal connector.
A modem is used for gaining internet through a RJ-11 port... (Phone lines) AKA Dial-Up = slow internet
Using the com port
Serial and USB ports are most often used to connect an external modem to a PC.
The Ethernet port is used to connect a computer to a connectivity device such as a modem, router, switch,etc. Does so via an ethernet cable.
One example is a serial modem, though somewhat outdated today.
In the past external modems connected to the COM (or serial) port. However, most modern external hardware is USB these days, modems are no exception.