An RJ11 connector with 4 pins is commonly used for telephone lines, especially for connecting a standard telephone to a wall jack or for DSL internet connections in some cases. RJ11 connectors are typically used for low-speed data transmission and voice communication.

Key features of an RJ11 4-pin connector:

• 4 Pins: The RJ11 connector can have anywhere from 2 to 6 pins, but for a 4-pin version, it typically supports two pairs of wires for the telephone line.
• Size: It is smaller than other connectors like RJ45, which is used for Ethernet networking.
• Compatibility: It works with telecommunication devices like landline telephones, fax machines, and sometimes broadband modems.

If you're working with an RJ11 4-pin connector, you will typically have to wire it according to the specific needs of your device or application, making sure to match the wiring configuration.