dmidecode reports 3 ports while I have only 2.

[Strong]

Extract from dmidecode output on my laptop Dell Inspiron 1501:

Handle 0x000E, DMI type 8, 9 bytes.
Port Connector Information
        Internal Reference Designator: J30
        Internal Connector Type: None
        External Reference Designator: Microphone In
        External Connector Type: Mini Jack (headphones)
        Port Type: Audio Port

Handle 0x000F, DMI type 8, 9 bytes.
Port Connector Information
        Internal Reference Designator: J30
        Internal Connector Type: None
        External Reference Designator: Line In
        External Connector Type: Mini Jack (headphones)
        Port Type: Audio Port

Handle 0x0010, DMI type 8, 9 bytes.
Port Connector Information
        Internal Reference Designator: J30
        Internal Connector Type: None
        External Reference Designator: Speaker Out
        External Connector Type: Mini Jack (headphones)
        Port Type: Audio Port

But I have only 2 ports on its side: mic and phones. So how I can use
the "Line In" safe way?