Component allows you use all 4 lines.
Each line can contain many remote clients, and also media resource, like a playing file.
But in same time only 1 line can be active - contain local client (as sample headphone+microphone).
Other lines can play file, receive DTMF, etc
Many components functions use current line as default.
Sample method "StartCall" tries make a call on current line.
Use method "SetCurrentLine" for switch betwen lines.

Concerning example, you can call components methods in following order:
SetCurrentLine(1)
StartCall(..)
SetCurrentLine(2)
StartCall(..)

Regarding playing files, you can play file for all clients joined in line.
SetCurrentLine(1)
PlayFile("1.wav")
SetCurrentLine(2)
PlayFile("2.wav")

Note: SDK can support as many phone lines as it is needed.