How to distinguish the RJ45&RJ11

User Application Requirement
Updated 06-27-2022 02:49:35 AM 123793

RJ stands for Registered Jack.


  • 8 Position
  • 8 Pin/Conductor (4/8 options)
  • Mainly used in network wiring.
  • 6mm * 11mm

Figure 1: RJ45 connector (male) Figure 2: RJ45 Jack (female)

Figure 6: RJ45-plug-jack-schematic


  • 6 Position
  • 4 Pin/Conductor (2/4/6 options)
  • Used for telephone, and (ADSL/VDSL) modem, etc.
  • 6mm * 9.5mm

Figure 4: RJ11 6P4C connector (male) Figure 5: RJ11 6P4C Jack (Female)

Figure 3: RJ-11-plug-jack-schematic

RJ45&RJ11 ports on TP-Link Modem Router

Figure 7: RJ11&RJ45 ports on TP-Link modem Router

The first 3 ports are RJ11 (6P6C/6P4C/6P2C) Jack. These ports are normally used with an RJ11 connector (telephone line).

The 4 yellow ports are RJ45 (8P8C/8P4C) Jack. These ports are normally used with an RJ45 connector (Ethernet cable).


Figure 8: RJ45&RJ11 Pairs Figure 9: RJ11 in real RJ45 in real

Table 1: Comparison between RJ45&RJ11


6P4C (6 positions, 4 conductors)

8P8C (8 positions, 8 conductors)


Phones, ADSL/VDSL lines, modem cables. RJ11 is mostly used for voice applications.

Computer networking. RJ45 is used in Ethernets or connecting cable/fiber modems or NBN box with Wi-Fi routers.


RJ11 connectors can support about 100+Mbps

RJ45 connectors can support up to 10Gbps over Ethernet, provided the other equipment like network cables also support that speed.

Shape and size

Compact, square-shaped

Longer, more rectangular


  • RJ45 is mostly used with Ethernet cables while RJ11 is connecting to telephone units.
  • RJ45 has 8 wires inside while Rj11 has 4 wires.
  • RJ45 is bigger in size than RJ11.
  • You cannot plug-in the RJ45 cable connector into an RJ11 jack/interface/port/slot, however, you can do the opposite. Plugging an RJ11 cable into an RJ45 jack/interface/port/slot is the most common mistake that might happen. It will not work by doing so and it might also damage the RJ45 port as power is being delivered by the telephone company into your handset that allows it to function even during a power outage.

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