Which device commonly uses an RJ-11 connector?

The device that commonly uses an RJ-11 connector is a telephone. RJ-11 connectors are the standard interface used for telephone wiring and are designed to connect telephones to telephone lines. It typically has four or six positions, but only two or four wires are utilized, making it suitable for the analog signals used in traditional telephone systems. This connection allows devices like telephones to communicate over the public switched telephone network (PSTN).

While modems can also use RJ-11 connectors to connect to a phone line for DSL services, the primary and most traditional device associated with RJ-11 is the telephone itself. Personal computers generally use different types of connectors such as USB or Ethernet for networking purposes, and monitors connect through HDMI or DisplayPort types, neither of which supports RJ-11 connectors. Thus, in the context of identifying a device primarily associated with RJ-11, the telephone is the most appropriate choice.