I tested the polarity and the coupler changes the polarity of the lines compared to when polarity checked at outlet before coupler used. PIN layout?

Yes, many of these couplers are simple, straight thru pin 2-5 to 2-5 and do not properly crossover/reverse the pins to maintain the continuity on the same wires throughout both cables. If using this type of straight thru coupler, you'll need to either use two of them (plus an extra "bridge" cable) or wire up your own custom crossover cable to correct the pin-out issue.

Does this work for two-line phones?

If there are two lines connected to the phone that you want to extend with "extension chords" (connect to longer phone lines), you would need on coupler for each line.

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RFAdapter RJ11 Coupler, 2 Pack Telephone Phone Line Connector Coupler RJ11 6P4C Inline Keystone Jack Female to Female Straight Telephone Cable Cord Extension White

Product ID: 378141472

Details

Brand
RFAdapter
Cable type
Telephone
Compatible devices
Telephone
Connector type
RJ11
Special features
Compact

⚡Low Signal Attenuation

📞6P4C Pin Configuration

🔌RJ11 Female-to-Female Connector

S$22

Duties & taxes included

In stock

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Description

📞 Connect smarter, sound clearer — never miss a call again!

CRYSTAL CLEAR AUDIO - Experience high-fidelity sound with strong anti-interference for flawless calls every time.
SEAMLESS LINE EXTENSION - Effortlessly connect and extend your telephone lines without signal loss or distortion.
UNIVERSAL COMPATIBILITY - Works flawlessly with all RJ11 devices—landlines, fax machines, and answering systems.
COMPACT DURABLE DESIGN - Space-saving, sturdy build fits discreetly in any home or office setup.
HASSLE FREE INSTALLATION SUPPORT - Plug-and-play setup backed by a 12-month worry-free warranty and responsive customer service.

The RFAdapter RJ11 Coupler 2-Pack offers a compact, durable solution to extend telephone lines with female-to-female RJ11 connectors. Featuring 6P4C pins and low signal attenuation, it ensures crystal-clear, interference-free audio. Compatible with all RJ11 devices, this easy-to-install coupler is perfect for home or office use, backed by a 12-month warranty and excellent customer support.

Specifications

ASIN	B08L67FQ8T
Best Sellers Rank	#57,625 in Electronics ( See Top 100 in Electronics ) #84 in Telephone Cables
Brand	RFAdapter
Brand Name	RFAdapter
Cable Type	Telephone
Cable type	Telephone
Color	White
Compatible Devices	Telephone
Compatible Phone Models	All Smartphone
Compatible devices	Telephone
Compatible phone models	All Smartphone
Connectivity Technology	RJ11
Connector Gender	Female-to-Female
Connector Type	RJ11
Connector type	RJ11
Customer Package Type	FFP
Customer Reviews	4.6 out of 5 stars 656 Reviews
Ethernet Cable Category	Cat 5
Indoor Outdoor Usage	Indoor
Item Shape	Round
Manufacturer	RFAdapter
Model	RFAdapter Telephone Wires
Number of Items	2
Number of Pins	6
Other Special Features of the Product	Compact
Part Number	ULRF0A0135A-2-CA
Recommended Uses For Product	telephone line extension or combination
Special features	Compact
UPC	744306795542
Unit Count	2 Count

Reviews

R**G

It works great

Did not have 1 long enough cord to connect phone/fax machine to phone jack but this coupler did great job of connecting the two cords.

12.06.2025

S**A

ELOGIO

Ótimo. Atendeu às minhas necessidades. Recomendo.

28.03.2025

A**Z

Satisfecho!

Buen producto

30.01.2026

E**R

Know what your source of the TIP and RING and on what pins each are located

If this product is used you need to know how your system is configure

18.10.2021

B**T

Connected

Couldn't find these anywhere else. Perfect for what I needed to extend my phone system. Very Happy.

20.12.2024

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