What a phone jack is and where you'll find one
A phone jack is the socket in your wall or on a device where a telephone cord plugs in. It looks like a small rectangular opening, usually white or beige, with six or eight tiny holes inside. The most common type in homes is the RJ11 jack, which has four or six holes and connects standard telephone cords. Older homes sometimes have larger jacks from the 1970s and 1980s, and some buildings still have the original four-prong jacks that required a special adapter.
Phone jacks appear in walls throughout your home — typically near where you want to use a phone, fax machine, or modem. They connect to telephone wiring that runs through your walls and eventually reaches the telephone company's network outside your house. If you're setting up a new phone line or moving an existing one, you'll either be plugging a cord into an existing jack or installing a new jack in the wall.
Key Takeaways
- A phone jack is a wall socket with four to eight small holes where a telephone cord plugs in, and the most common household type is the RJ11 jack.
- To connect a phone, simply insert the flat rectangular connector at the end of the phone cord into the jack until it clicks — no tools or special knowledge required.
- If you need a jack in a new location, you can use a surface-mounted jack that screws to the wall and connects to existing telephone wiring, or hire an electrician to run new wiring inside the walls.
- Telephone jacks and network jacks (Ethernet) look similar but are not interchangeable — a phone jack is slightly smaller and has a different connector shape.
Plugging a phone cord into an existing jack
If a jack is already installed in your wall, connecting a phone is straightforward. Take the flat rectangular connector at the end of your phone cord — it will be slightly wider than a network cable connector — and push it straight into the jack opening. Push until you hear or feel a small click, which means the connector has seated properly and the tiny clips inside the jack have locked it in place.
The connector will only fit one direction, so you don't need to worry about inserting it backwards. If it doesn't slide in smoothly, don't force it — check that you're pushing straight in and that the connector isn't bent or damaged. Once it's clicked in, your phone should have a dial tone (if it's connected to an active phone line) or be ready to use with your service provider's equipment.
To remove the cord, gently press the small tab or clip on the connector while pulling the cord out. The tab is usually on the top or bottom of the connector and prevents the cord from accidentally falling out.
Installing a surface-mounted jack in a new location
If you need a phone jack somewhere your home doesn't have one, the easiest option is a surface-mounted jack — a small plastic box that screws to the wall and connects to existing telephone wiring. You'll need a screwdriver, the surface-mount jack kit (available at hardware stores for $10 to $20), and access to the telephone wiring that runs through your walls.
First, locate where the telephone wiring enters your home — usually in a basement, attic, or utility closet. You'll see a larger junction box called the network interface device or demarcation point, which is where the telephone company's line meets your home's wiring. From there, telephone wire runs to existing jacks throughout your house. You can follow this wire to find a path to your new location, or run a new wire from the junction box if the existing wire doesn't reach.
Once you've decided where to mount the jack, screw the plastic box to the wall at that location. Strip about half an inch of insulation from the telephone wire using a wire stripper, then insert the exposed wires into the small terminals inside the jack box — the color order doesn't matter for a single phone line, but if you're connecting to existing wiring, match the colors to what's already there. Screw the terminals tight, then test by plugging in a phone and checking for a dial tone.
When to hire an electrician or telephone technician
If the existing telephone wiring in your home doesn't reach the location where you need a jack, or if you're uncomfortable working with the wiring yourself, hire a licensed electrician or telephone technician. They can run new wiring inside your walls, which looks neater than surface-mounted boxes and is the standard for new construction or major renovations.
You should also call a professional if you're not sure whether the wiring in your home is active or connected to a working phone line. Telephone wiring is low-voltage and safe to touch, but a technician can confirm that your setup is correct and that the line is properly grounded.
Phone jacks versus network jacks — why they're not the same
A network jack (also called an Ethernet jack or RJ45) looks very similar to a phone jack but is slightly larger and has eight holes instead of four or six. The connectors are different sizes and shapes, so a phone cord will not fit into a network jack, and a network cable will not fit into a phone jack. If you plug a phone cord into the wrong type of jack, it simply won't connect.
In older homes, you may find only phone jacks. In newer homes built after the 1990s, you'll usually find both — phone jacks for telephone service and network jacks for internet. If you need to convert a phone jack to a network jack (or vice versa), you'll need to replace the jack itself, not just the cord.
Troubleshooting a phone jack that doesn't work
If you've plugged a phone into a jack and there's no dial tone, first check that the phone itself works by plugging it into a different jack you know is active. If the phone works elsewhere, the problem is with that particular jack or the wiring connected to it.
Next, check the telephone line at the network interface device (the large box where the phone company's line enters your home). Make sure all the wires are firmly seated in their terminals and that none are loose or corroded. If the wires look fine but the jack still doesn't work, the problem may be a break in the wiring between the junction box and the jack — this usually requires a technician to locate and repair.
If multiple jacks in your home have stopped working at the same time, the problem is likely with the main line coming from the telephone company, not with your home's wiring. Contact your phone service provider to report the outage.
Frequently Asked Questions
Can I use a phone jack for internet?
No. A phone jack carries telephone signals, and a network jack carries internet signals — they use different wiring and connectors. However, some devices like modems have both a phone jack input (to receive the signal from the phone line) and a network jack output (to send internet to your computer). The modem itself bridges the two.
Is it safe to touch the wires inside a phone jack?
Yes. Telephone wiring carries very low voltage — around 48 volts — which is not dangerous to touch. You won't get shocked. However, if you're working with the main telephone line coming from outside your home, it's best to let a professional handle it, as the incoming line may carry higher voltage.
What if my phone cord doesn't fit in the jack?
The connector may be damaged or bent. Inspect the flat connector at the end of the cord for cracks, bent pins, or debris. If it looks damaged, the cord needs to be replaced. If the connector looks fine, try a different phone cord in the same jack to confirm the jack itself isn't the problem.
Do I need a special jack for a fax machine or modem?
No. A standard phone jack works for any device that uses a telephone line — phones, fax machines, modems, and alarm systems all use the same RJ11 jack. The device itself determines what it does with the signal, not the jack.
Can I install a phone jack myself, or do I need a technician?
You can install a surface-mounted jack yourself if you're comfortable with basic wiring and have access to existing telephone wiring. If you need wiring run inside your walls or you're unsure about the existing setup, hire a professional. The cost of a technician visit is usually $100 to $200 and saves you from potential mistakes.