4-Wire Phone Jack Wiring Diagram (RJ11 / RJ14)

This is a free printable 4 wire phone jack wiring diagram: download the diagram as SVG or open it and print to paper or PDF.

Wire a 4-wire telephone jack for single-line RJ11 or dual-line RJ14 connections using the standard colour code: red and green for Line 1, yellow and black for Line 2.

A standard telephone wall jack in North America and many other markets uses a 4-wire modular connector system. The connector body is the familiar 6-position modular connector (commonly called RJ11 when used for a single line, or RJ14 when wired for two lines). Despite the 6-position body, telephone applications typically use only the inner 4 positions — positions 3, 4, 5, and 6, counting from left to right with the connector latch facing away from you.

The conventional 4-wire colour code for telephone wiring is: green (Tip, Line 1 positive), red (Ring, Line 1 negative), black (Tip, Line 2 positive), and yellow (Ring, Line 2 negative). Line 1 uses the green and red pair; Line 2 uses the black and yellow pair. The terms Tip and Ring originate from the days of manual telephone switchboards, where the tip and ring of the physical phone plug carried the two conductors of the telephone pair.

For a single-line telephone connection (RJ11), only Line 1 is used: green to the centre pin position (pin 4 in a 6P6C, the inner pair) and red to its paired position (pin 3). The yellow and black conductors for Line 2 are either not present or left unconnected.

For a two-line connection (RJ14), all four conductors are used. The jack body is the same physical 6-position connector, but pins 2 and 5 (the outer pair of the inner four positions) carry Line 2 — black on pin 2 and yellow on pin 5. This allows a 2-line telephone or fax machine to access both lines from a single wall jack.

In wiring from the telephone company's network interface device (NID) or distribution block inside the building, the 4-conductor cable typically uses solid blue/white-blue, orange/white-orange twisted pair (CAT3 or standard telephone cable), which is colour-mapped to the conventional station wiring colours at the jack terminals. In older installations, 4-conductor flat cable (quad cable) with solid red, green, yellow, and black conductors is common.

How to wire 4 wire phone jack wiring diagram

1. Identify the cable type and conductor count Examine the cable running to the telephone jack location. Traditional telephone quad cable contains 4 solid conductors: red, green, yellow, and black. Structured wiring CAT3 or CAT5 cable contains twisted pairs with different colour coding. Count the conductors and identify the cable type before purchasing the jack, as some jacks use screw terminals and others use 110-type punch-down contacts.
2. Remove the existing jack faceplate (if replacing) Unscrew the faceplate from the wall backbox. Note which wire colour is connected to which terminal before disconnecting anything. Take a photograph if you are unsure you will remember. Disconnect the wires from the old jack terminals.
3. Identify jack terminals for Line 1 On the replacement jack, locate the terminals marked for Line 1 (or the two centre terminals if the jack uses a general screw terminal arrangement). Line 1 Tip terminal receives the green conductor. Line 1 Ring terminal receives the red conductor. These are the most commonly used connections — they serve a standard single-line telephone.
4. Connect Line 1 conductors (green and red) Connect the green conductor (Line 1 Tip) to the Line 1 Tip terminal of the jack — often marked TIP 1, T1, or colour-coded green on the jack body. Connect the red conductor (Line 1 Ring) to the Line 1 Ring terminal — marked RING 1, R1, or colour-coded red. Tighten screw terminals firmly, or use the punch-down tool for 110-type contacts.
5. Connect Line 2 conductors (black and yellow) if applicable If wiring for a second line, connect the black conductor (Line 2 Tip) to the Line 2 Tip terminal (marked TIP 2, T2, or outer position). Connect the yellow conductor (Line 2 Ring) to the Line 2 Ring terminal (RING 2, R2). If only Line 1 is required, leave the Line 2 terminals unconnected.
6. Dress the cable and mount the faceplate Fold excess cable neatly into the backbox without creating sharp bends near the terminal connections. Ensure no bare conductor is exposed outside a terminal. Mount the faceplate securely. Do not use excessive force — many telephone jack faceplates use plastic screw mounts that are easily stripped.
7. Test the jack with a telephone or line tester Plug a known-working telephone into the jack and listen for dial tone on Line 1. For a 2-line jack, test Line 2 using a 2-line telephone or by testing with a telephone that has a line select button. A modular handset tester (line tester) can confirm Tip/Ring voltage and line polarity without needing an active call.

Specifications

Safety warnings

• The telephone line carries a nominal -48V DC with approximately 90V AC ringing voltage superimposed when the line is ringing. While not typically lethal to healthy adults, this voltage can cause a significant and painful shock, particularly the ringing voltage. Do not work on telephone wiring while a call is active or while the line may ring — or work with the network interface device (NID) disconnected.
• Do not confuse telephone cabling with mains electrical wiring. 4-wire telephone cable is not rated for mains voltage. Never run telephone cable in the same conduit or wiring channel as mains wiring, and never connect a telephone jack to a mains electrical circuit under any circumstances.
• In some jurisdictions, connecting equipment to the telephone network requires that the equipment be type-approved (e.g., FCC Part 68 in the US). Improperly connected equipment can cause interference on the public telephone network. Ensure any equipment connected is approved for use with the local network.
• This is an illustrative reference for informational purposes. Telephone wiring standards and permitted DIY activities vary by jurisdiction and network operator. In some markets, internal telephone wiring beyond the network interface device (NID) is the customer's responsibility; in others, it must be carried out by the network operator or licensed cabling technician.

Tools needed

• Small flat-blade screwdriver (for screw-terminal jacks)
• 110-type punch-down impact tool (for IDC-type jacks and distribution blocks)
• Wire strippers sized for 24–26 AWG solid conductors
• Modular crimp tool (if field-terminating modular plugs on cord ends)
• Telephone line tester or working telephone handset (for continuity and line testing)
• Scissors or knife (for trimming cable jacket without nicking conductors)

Common mistakes

• Swapping green and red (reversing Tip and Ring polarity on Line 1): Many telephones and modems are polarity-sensitive. Reversed polarity can cause one-way audio, failure to receive calls, or modem authentication failures. Always connect green to Tip and red to Ring.
• Connecting yellow to Line 1 instead of Line 2: Yellow is the Ring conductor for Line 2, not a spare or earth wire. Incorrect identification causes Line 2 to be missing or Line 1 to be wired incorrectly. Verify conductor identity before connecting.
• Using a single-line (RJ11-wired) jack where two lines are needed: A jack wired only with green and red on the centre pins will not pass Line 2 signals. If a 2-line telephone or fax machine shows 'Line 2 unavailable', check whether the jack is wired for 2 lines.
• Not seating the conductor fully into punch-down IDC contacts: An incompletely punched-down wire rests on the insulation rather than piercing it, creating an open circuit. The punch-down tool must be pressed firmly until the conductor bottoms out and the cut blade (if using cut mode) trims the excess cleanly.
• Confusing CAT5 colour codes with traditional telephone colour codes: CAT5 cable uses blue/white-blue and orange/white-orange pairs — these must be mapped to telephone functions (Tip/Ring for Line 1 and Line 2) at the terminal. Treating CAT5 colours as if they were standard telephone quad colours produces incorrect wiring.

Troubleshooting

No dial tone at the jack

Cause: Open circuit in Line 1 wiring — disconnected green or red conductor at jack terminals, break in the cable, or Line 1 not active at the network interface device Fix: Test the line at the network interface device (NID) — plug a telephone into the test jack on the NID. If dial tone is present at the NID but not at the wall jack, the fault is in the internal wiring. Trace the cable path and test for continuity on both green and red conductors between the NID and the jack.

One-way audio on telephone calls — caller or callee cannot be heard

Cause: Open circuit on either the Tip (green) or Ring (red) conductor, causing only one side of the differential telephone pair to be connected Fix: Test continuity on both the Tip (green) and Ring (red) conductors separately. An open on either one causes degraded or one-sided audio. Check terminal connections at both the jack and the distribution point.

Line 2 does not work on a 2-line telephone

Cause: Jack is wired for single line only (only green/red connected), or black/yellow conductors are not terminated correctly at the jack or the distribution point Fix: Open the jack faceplate and verify that black and yellow conductors are connected to the Line 2 terminals (pins 2 and 5 of the modular connector body). If only green and red are connected, the jack is a single-line RJ11 — replace with an RJ14-wired jack or add the Line 2 connections.

Frequently asked questions

What is the difference between RJ11 and RJ14?

Both use the same physical 6-position modular connector body. RJ11 wires only the two centre positions (pins 3 and 4) for a single telephone line — green and red. RJ14 wires all four inner positions (pins 2, 3, 4, and 5) for two telephone lines — red/green for Line 1 and black/yellow for Line 2. An RJ11 plug can physically mate with an RJ14 socket and will use Line 1.

Which wire is positive and which is negative in a telephone jack?

In telephone circuits, the terms Tip and Ring are used rather than positive and negative. Tip is the positive conductor — green for Line 1, black for Line 2. Ring is the negative conductor — red for Line 1, yellow for Line 2. In North American standard telephone wiring, Tip is approximately -48V DC with respect to ground, and Ring is at or near ground potential (the polarity is opposite to what the colour names imply — this is historical convention).

Why is the telephone line voltage negative?

The public switched telephone network (PSTN) uses a -48V DC battery supply at the central office, with the negative terminal connected to the Tip conductor and positive to Ring. This polarity convention is maintained throughout the network to prevent electrolytic corrosion on the copper pair. The magnitude is 48V on hook and drops to approximately 6–12V when the line is off-hook (in use).

Can I use a CAT5 or CAT6 ethernet cable for telephone wiring?

Yes — CAT5 and higher twisted-pair cable works well for telephone wiring. The pairs within CAT5 cable are colour-coded differently (blue/white-blue, orange/white-orange, etc.) from traditional telephone quad cable, but can be mapped to telephone line functions at the jack terminals. Using twisted pair cable rather than flat quad cable improves noise rejection on longer runs.

How do I wire a 2-line telephone jack if I only have 2-wire cable from the wall?

You cannot support 2 lines from a single 2-wire cable — two separate lines require four conductors. You either need a 4-conductor cable run to the jack, two separate 2-wire cables (one per line), or a structured telephone wiring system that distributes multiple lines from a central distribution point. Check the cable already in the wall for the number of conductors before purchasing a 2-line jack.

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