Sony PCV-RX480DS - Manual (Page 93)

Fax/Modem Card 79
Lucent 1648 Modem
There are two RJ-11 jacks: one to connect a telephone line, and one to
connect a phone.
Connectors
Name Connector Type Description
Telephone RJ-11 Connects to phone
Line RJ-11 Connects to telephone line
Telephone
Line