Telephone Jack VS. Ethernet Jack

Telephone Jack VS. Ethernet Jack: What’s The Difference?

Whether you want an ethernet or telephone cable for your connections, the most important thing is a good signal. You can use telephone jacks or ports and Ethernet jacks to connect devices to a network, but each has unique qualities, and you may be trying to compare a telephone jack and an ethernet jack.

The key difference between these two is that:

  • The telephone jack connects a telephone to a wall outlet, while the ethernet jack connects computers and other devices to an Ethernet cable. They look the same but have different uses.
  • The ethernet jack accepts an RJ45 connector, while the telephone jack accepts RJ11 and RJ12 connectors.

In this article, I’ll outline the differences between the two jacks and how you can explore their functionalities.

Key Specs Telephone Jack

Ethernet Jack

Function Voice communication Data transmission
Installation Mounted on walls Found in computers, smart TVs, etc.

Also mounted on walls.

Size 3.5mm 5.8mm
Connectivity Has RJ11, and RJ12 connectors Have RJ45 connectors
Conductivity Uses 4 or 6 conductors Uses 8 conductors
Cabling Accepts phone cables Accepts ethernet cables
Price About $6 (Less Expensive) About  $10 (More Expensive)
Connector Size Physically smaller Physically bigger
Convertibility Can be converted to an Ethernet jack Cannot be converted to a phone jack
Transmission speed Has a lower speed Has a faster speed
Bandwidth Has a smaller bandwidth Has a larger bandwidth
Plug The plug is flat and small The plug is thick and round

What Is A Telephone Jack?

A telephone jack is a modular connector that lets you connect your phone line to an electrical outlet. The telephone jack accepts two cables and has two parts: the plug and the socket. The plug has a blade-like shape and fits into your phone’s port.

The socket is a hole in the wall where you can insert the plug from your phone line. Most homes in North America have at least one telephone jack in the wall near their telephone.

They’re usually located next to each other in a small plastic box on the wall. This box is called a “telephone outlet” or “telephone junction.”

Although it’s designed for voice communications, you can convert the telephone jack into an ethernet jack.

What Is An Ethernet Jack?

An ethernet jack or LAN port is a socket that allows you to connect your computer to a network. It’s used mainly for connecting to the internet, but you can use it for local area networks (LANs). The cable has eight wires that carry data from your computer to the network.

The plug on the end of the line is called an RJ45 connector, and it looks like a telephone jack but is slightly bigger. Desktop computers and laptops often come with in-build ethernet jacks for internet connectivity.

The inbuilt Ethernet jack is connected to the computer’s ethernet card, which is attached to the motherboard. You can find them on walls in modern houses.

Telephone Jack And Ethernet Jack | All The Differences

Wiring a Home Phone jack

The main difference between an Ethernet and a telephone jack is that one is designed to connect computers. In contrast, the telephone jack is designed to connect or use a telephone cable. Other differences are:

  • Telephone jack connectors (RJ11 and RJ12) have 4 or 6 pins depending on the connection type. The 4-pin version connects two devices, while the 6-pin version can connect more than two devices in a series.
  • The ethernet jack is found in computers, servers, and smart TVs and has 8 pins. It has different speeds ranging from 10 Mbps and 100 Mbps. Gigabit ethernet has a speed of 1,000 Mbps.
  • The two types of jacks are not interchangeable, but it is possible to convert one into the other using adapters purchased at most electronics stores. The process does not require special tools but takes time and skill.


Ethernet jacks are used for network connections on smart devices like computers, servers, etc., or in a building.

The telephone jack is used for connecting phone line sets in a building. It is for voice communication.

The two types of jacks are not interchangeable, but it is possible to convert one into the other using adapters purchased at most electronics stores.


Telephone jack connectors (RJ11 and RJ12) have 4 or 6 pins depending on the connection type. The 4-pin version connects two devices, while the 6-pin version can connect more than two devices in a series.

Ethernet jacks have RJ45 connectors consisting of 8 pins. This nature allows them to transmit data signals.


The ethernet jack is found in computers, servers, and smart TVs. You can also install them on walls.

You can only install a telephone jack on walls in homes or offices.


Telephone jacks look similar to ethernet jacks, but the sizes are different. An ethernet jack is larger because it has 8 pins. Telephone jacks have 4 or 6, so they’re smaller.


The telephone jack coupler is cheaper than ethernet jack couplers, but they’re not expensive. You can find an RJ11 coupler at just $6, but an ethernet jack comes at $10.

Can You Use The Telephone Jack For The Internet?

No, a telephone jack cannot be used for the internet without additional equipment or modifications. Telephone jacks are designed for analog voice signals and operate at a much lower frequency than those used for internet communication.

In order to use a telephone jack for internet access, an analog modem would be needed to convert the digital signals used for internet communication into analog signals that can be transmitted over the phone lines. However, this method is slow and outdated, and most internet providers use digital signals that require a broadband connection, such as cable or fiber optic internet.

Another way is by joining an RJ45 connector to the phone jack, a simple DIY.

How To Convert A Telephone Jack To An Ethernet Jack

RJ45 Network Patch Cables

If you are trying to switch from a telephone to an ethernet jack, follow the step-by-step method below:

Method 1: Using DSL Modem

A DSL modem is a device that connects to your computer via an Ethernet cable and provides you with access to the internet. The DSL modem is connected to your local telephone service provider, providing you with Internet access on your computer.


  • Connect the DSL modem to power by plugging the electric DSL’s power supply cord into the wall socket.
  • Insert the plug at one end of the modular telephone cord into the telephone jack socket.
  • Insert the other end into the socket labeled “DSL” on the back of the DSL modem.
  • Insert the ethernet plug at one end of the ethernet cable into the socket labeled network at the rear of the DSL modem.

Method 2: Changing The Connector

The old RJ11 phone jacks you probably have in your home are getting replaced by the new RJ45 ethernet jacks.

  • You’ll need a data connector that converts the old telephone jack into an Ethernet jack. You can get one at your local electronics store or on Amazon.
  • Use a screwdriver to remove the wall panel covering the telephone jack.
  • Pull out the phone cable; it’s likely a Cat5, Cat5e, or Cat6 cable; you can tell from the colors.
  • Match the colors on the telephone wire(s) to the colors on the data connector and insert them into their slots.
  • Cut off loose ends and reinsert the cable.
  • Reinstall the wall panel.

So, which one should you go for?

Answering the question of telephone jack vs. ethernet jack, which you should go for, is not so complex. It depends on what you hope to achieve.

The ethernet jack is perfect for internet connections, while a telephone jack is ideal for a telephone connection.

If you built your house over 50 years ago, you’d have a telephone jack(s) on your walls. You can convert them into ethernet jacks and use them for internet connections. Alternatively, install an RJ45 jack on your wall.

You May Want To Know

Can You Plug An Ethernet Cable Into A Phone Jack?

You cannot plug an ethernet cable directly into the telephone jack because it is not wired for telephone service. You can plug an Ethernet cable into a DSL, cable modem, or even your router if it has an Ethernet port.

The problem with using a phone jack for internet access is that it’s not meant for that purpose. The phone cable has a low bandwidth, so it cannot send high-speed internet traffic.

What Is A Telephone Wall Jack Called?

The telephone wall jack is called Registered Jack in the US. It’s why we have RJ11, RJ12, and RJ45. The Federal Communications Commission licenses the phone jacks.

Most telephones in the United States are connected to the wall via a four-pin RJ11 plug, which plugs into the telephone wall jack.

Are RJ11 And RJ45 Connectors Different?

Yes, RJ11 and RJ45 connectors are different. While both connectors are used for telecommunications connections, they have different sizes and numbers of contacts.

RJ11 connectors are typically used for connecting telephone lines and have four contacts arranged in a single row. They are smaller than RJ45 connectors and are not compatible with Ethernet connections.

RJ45 connectors, on the other hand, are used for Ethernet connections and have eight contacts arranged in two rows. They are larger than RJ11 connectors and are not compatible with telephone connections.

Where Is RJ45 Used Besides Ethernet Jack?

RJ45 is found on most computers and networking devices with ethernet jacks and other applications where twisted pair cables are required.

For example, it’s often used in telephone systems and audio/video installations because these applications require twisted pair cabling for maximum performance.

Is RJ11 Better Than RJ12 For Telephone Jack?

RJ11 and RJ12 connectors are similar in size and shape, and both can be used for telephone connections. However, RJ11 connectors are more commonly used for telephone connections and are typically considered to be the better option.

The main difference between RJ11 and RJ12 connectors is the number of contacts. RJ11 connectors have four contacts arranged in a single row, while RJ12 connectors have six contacts arranged in two rows. While RJ12 connectors may provide slightly better signal quality due to the additional contacts, they are less commonly used for telephone connections and may not be compatible with all devices.

Is RJ11 a 4-wire?

Is RJ11 a 4-wire

Yes, RJ11 connectors typically have four wires. These connectors are commonly used for telephone connections and have four contacts arranged in a single row. The wires are typically color-coded and correspond to specific functions, such as the transmission and reception of signals.

While RJ11 connectors may have additional contacts or wires in some cases, they typically have four wires for standard telephone connections.

What voltage is RJ11?

RJ11 connectors do not have a specified voltage. They are simply a type of connector that is commonly used for telephone connections. The voltage used for telephone lines depends on the specific application and the location and can vary widely.

For example, in the United States, standard residential telephone lines typically use a voltage of around 48 volts DC, while commercial telephone lines may use higher voltages or AC power.

It’s important to use appropriate voltage levels and follow electrical safety guidelines when working with telecommunications equipment and wiring.

How far can you run RJ11?

The maximum distance that you can run an RJ11 cable depends on several factors, including the quality of the cable and the specific application.

For standard telephone connections, which use low-frequency signals, the maximum distance for an RJ11 cable is typically around 100 meters (328 feet). However, this distance may be reduced if the cable quality is poor or if there are other sources of interference, such as electrical or radio frequency interference.


As you can see from this phone jack versus Ethernet comparison, the two lines have some differences, which is why they are better suited for different applications. The key distinction is that Ethernet employs an RJ45 connector with 8 pins, whereas phone jacks employ an RJ11/RJ12 connector with 4-6 pins. The difference in pins and connectors results in a size difference, with a phone jack being slimmer.

Considering their advantages, a phone jack is preferable for phone connections, whereas Ethernet is best for internet connectivity, particularly due to its speed. But, bear in mind that there are various types of Ethernet connections accessible, so make sure you select one based on your needs.

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