Phone Line Wiring Diagram: RJ11 Colour Codes, Line 1 and Line 2 Connections

Phone Line Wiring Diagram: RJ11 Colour Codes, Line 1 and Line 2 Connections — interactive diagram. Open it in the editor to customise components and wiring.

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

A phone line wiring diagram shows how the tip and ring conductors of a PSTN or DSL telephone line are routed from the network interface to RJ11 sockets and extension outlets throughout a building.

The public switched telephone network (PSTN) delivers a single telephone line to a premises over two conductors called the tip and ring. These names originate from the tip and ring contacts of the early telephone switchboard plug. In modern practice, the tip conductor is the positive polarity conductor (with respect to the phone company equipment), and the ring is the negative polarity conductor. The DC voltage present on a quiescent telephone line is approximately 48 V DC (tip negative with respect to ring at the central office, reversed at the subscriber end depending on convention) and drops to approximately 6–12 V when a telephone goes off hook and current flows.

In North America, the standard four-conductor telephone cable uses the following colour conventions for the two most common line assignments:

Line 1 tip: green Line 1 ring: red Line 2 tip: black Line 2 ring: yellow

The green and red pair carry the first telephone line and are the standard pair for a single-line residential service. The standard RJ11 connector (6-position, 2-conductor) uses the centre two pins (pins 3 and 4 in a 6-position numbering where pin 1 is the leftmost) for Line 1. An RJ14 connector uses four conductors to carry both Line 1 and Line 2.

For DSL (digital subscriber line) service, the same copper pair carries both the voice PSTN signal and the DSL broadband data signal simultaneously, separated by the DSL modem's built-in splitter or by a standalone DSL filter (microfilter) installed at each telephone outlet. Without a DSL filter on telephones, the DSL signal causes an audible hissing noise on voice calls, and telephone handsets can attenuate the DSL frequency components.

Wiring extension telephone outlets from the network interface or the master socket in series (daisy-chain) is simple but each added outlet marginally increases the ringer equivalence number (REN) load. Exceeding the maximum REN specified by the network provider (typically 4 in the UK and Australia) will prevent some or all connected phones from ringing when an incoming call arrives.

How to wire phone line wiring diagram

Locate the network interface device (NID) or master socket The network interface device (North America) or master socket (UK) is the point of demarcation between the telephone company's wiring and the customer's internal wiring. In North America, the NID is typically a weatherproof box on the exterior of the building. In the UK, the master socket is a BT-type NTE5 or equivalent socket, usually near the point of cable entry.
Identify the incoming pair colour code Open the customer-access portion of the NID or remove the master socket faceplate. Identify the incoming pair — in North America, green (tip) and red (ring) for Line 1. In the UK, incoming pairs follow the BT colour code: blue/white (ring) and orange/white (tip) for the first pair in the external cable, though the internal wiring typically uses a different convention.
Plan the extension wiring layout Decide whether to wire extensions in a star topology (all extensions wired back to a central distribution point) or a daisy-chain (series). Star wiring is preferred for DSL services because it minimises the total wire length and simplifies fault isolation. Calculate the total REN of all devices to ensure it does not exceed the line maximum.
Install cable between the NID/master socket and extension outlets Run 2-pair (4-conductor) telephone cable between the distribution point and each extension outlet location. For hidden routing, use a cable drill and fish tape to route through walls and ceilings. In the UK, do not run telephone cable parallel to mains electrical wiring for extended runs — maintain a minimum 50 mm separation.
Terminate at the extension outlet Connect the tip conductor (green for Line 1 in North American cable) to the tip terminal of the outlet, and the ring conductor (red) to the ring terminal. In the UK, follow the outlet manufacturer's terminal labelling. Trim conductors to the correct length so no bare copper is exposed outside the terminal.
Install DSL microfilters if DSL service is present Plug a DSL microfilter into each telephone outlet before connecting any telephone handset. The DSL modem connects directly to the filtered outlet's modem port or directly to the line without a microfilter. Confirm that the microfilter is the correct type for the outlet fitting in use.

Specifications

PSTN line DC voltage (quiescent)	Approximately 48 V DC
PSTN line DC voltage (off hook, loop current flowing)	Approximately 6–12 V
Ringing voltage (North America)	Up to 90 V AC, 20 Hz
Line 1 tip conductor (North America)	Green
Line 1 ring conductor (North America)	Red
RJ11 Line 1 pins (6-position connector)	Pins 3 (tip) and 4 (ring)
Maximum REN per line (UK, typical)	4
Voice band frequency range	300 Hz – 3400 Hz

Safety warnings

Telephone line conductors carry DC voltages of approximately 48 V on a quiescent line and ringing voltages up to 90 V AC at 20 Hz. These voltages can cause a painful shock, particularly the ringing voltage. Do not handle telephone line conductors without first confirming no active call is in progress and the line is not ringing.
Do not work on the network side of the NID or master socket. The incoming telephone cable is the telephone company's property and infrastructure. Accessing the network side requires authorisation from the network operator and may be illegal or void the telephone service contract.
In the UK, internal telephone wiring work is generally permitted by the end user, but any work on the master socket's internal module requires BT Openreach (or the relevant network operator) approval. Check the applicable terms of service.
Do not run telephone cable in the same conduit or bundle as mains electrical wiring. Inductive coupling from mains wiring can introduce noise into the telephone signal and may pose a hazard if mains insulation is damaged.

Tools needed

Telephone cable punch-down tool or small flat screwdriver (for IDC terminals)
RJ11 crimping tool (if terminating modular plugs)
Wire strippers
Non-contact voltage tester (to confirm no mains voltage present on route)
Continuity tester or multimeter
Cable drill and fish tape for concealed routing
Cable staple gun or tacker

Common mistakes

Reversing the tip and ring conductors at a single extension outlet — the telephone will typically still work (most telephone equipment is polarity insensitive) but DSL equipment may fail or perform poorly.
Exceeding the maximum REN by connecting too many telephone handsets, preventing incoming calls from ringing at some or all extension outlets.
Connecting the DSL modem through a microfilter rather than directly to the line, which attenuates the DSL signal and severely degrades broadband performance.
Using excessive cable lengths on DSL installations — every metre of internal wiring adds resistance and capacitance that degrades DSL sync speed and stability.
Running telephone cable stapled to the same stud bay as mains wiring, causing noise pick-up on the telephone line and potential DSL interference.

Troubleshooting

No dial tone at an extension outlet: Cause: Open circuit in the tip or ring conductor between the NID and the extension, incorrect termination at the outlet, or the extension outlet has been wired to an unused pair. Fix: Use a continuity tester to verify the tip and ring conductors are intact from the NID to the outlet. Confirm the correct pair is terminated at both ends. Check that the NID customer-side connections are secure.
DSL broadband speed is significantly below expected: Cause: DSL modem connected through a microfilter, excessive internal cable length, or interference from electrical wiring. Fix: Connect the DSL modem directly to the line without a microfilter. Minimise internal wiring length by connecting the modem as close to the master socket as possible. In the UK, consider using the master socket test socket (behind the faceplate) to isolate the modem from extension wiring entirely.
Audible hissing or broadband noise on telephone voice calls: Cause: Missing or faulty DSL microfilter on the telephone handset outlet, allowing DSL frequencies to reach the telephone. Fix: Install a new, correctly rated DSL microfilter between the outlet and the telephone handset. Confirm the microfilter is oriented correctly (the telephone plugs into the microfilter's phone port, not the modem port).

Frequently asked questions

What are the tip and ring wires in a telephone line?

Tip and ring are the two conductors of a telephone line, named after the tip and ring contacts of the manual telephone switchboard plug. In North American cable colour coding, the tip conductor for Line 1 is green and the ring conductor is red. These two conductors carry the DC loop current (when off hook), the ringing voltage (up to 90 V AC at 20 Hz), and the audio signal.

Which pins does Line 1 use in an RJ11 connector?

In a standard 6-position RJ11 connector viewed from the clip side with the latch away from you, Line 1 uses pin 3 (tip, green) and pin 4 (ring, red) — the two centre pins. An RJ14 connector adds Line 2 on pins 2 (tip, black) and 5 (ring, yellow), the next pair outward from centre.

What is a DSL microfilter and where should it be installed?

A DSL microfilter (also called a splitter or line filter) is a small passive filter installed at a telephone wall socket to block the high-frequency DSL data signal from reaching the telephone handset. It should be installed at every telephone outlet that has a telephone connected to it. The DSL modem itself connects directly to the line without a microfilter.

What is the ringer equivalence number (REN)?

The ringer equivalence number (REN) is a measure of the loading that a telephone device places on the telephone line when ringing. Each telephone line has a maximum REN (typically 4 in the UK and Australia, varies by carrier in North America). The sum of all connected devices' REN values must not exceed the line maximum, or some or all phones will fail to ring on an incoming call.

Can telephone wiring carry both PSTN voice and DSL simultaneously?

Yes. DSL technology uses frequencies well above the voice band (typically from 25 kHz to over 1 MHz) on the same copper pair as the PSTN voice service (300 Hz to 3400 Hz). A splitter at the network interface or a microfilter at each telephone outlet separates the two frequency ranges, allowing simultaneous voice and data operation without interference.

Related diagrams

Free electrical calculators

Edit this diagram free in the online editor