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

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 & Anti-Interference

📞6P4C Pin Configuration for Clear Signal

🔌RJ11 Female-to-Female Connector

฿809

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Sold byAmazon ThailandDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

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Description

📞 Connect with Confidence — Extend Your Reach, Not Your Frustration!

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 - Sleek, space-saving form factor built to last in any home or office setup.
CRYSTAL CLEAR AUDIO QUALITY - High-fidelity sound with strong anti-interference ensures every call is crisp and clear.
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 for accurate signal transmission, it guarantees high-fidelity sound with minimal interference and signal loss. Universally compatible with all RJ11 devices, this coupler is perfect for home or office use, delivering easy installation and backed by a 12-month warranty for peace of mind.

Specifications

Asin	B08L67FQ8T
Best Sellers Rank	#66,322 in Electronics (See Top 100 in Electronics) #111 in Telephone Cables
Brand Name	RFAdapter
Cable Type	Telephone
Color	White
Compatible Devices	Telephone
Compatible Phone Models	All Smartphone
Connectivity Technology	RJ11
Connector Gender	Female-to-Female
Connector Type	RJ11
Customer Package Type	FFP
Customer Reviews	4.6 4.6 out of 5 stars (659) 4.6 out of 5 stars
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
Unit Count	2 Count
Upc	744306795542

Reviews

User

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

User

ELOGIO

Ótimo. Atendeu às minhas necessidades. Recomendo.

28.03.2025

User

Satisfecho!

Buen producto

30.01.2026

User

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

User

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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Yes, all products are sourced directly from authorized retailers in the US, UK, UAE and India. We maintain strict quality control processes and verify each product before shipping. All items come with applicable manufacturer warranties and are covered by our standard return policy.

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฿809

Duties & taxes included

In stock

Sold byAmazon ThailandDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

Buyer Protection · Full refund if your order doesn't arrive as described.

Desertcart purchases this item on your behalf and handles shipping, customs, and support to Thailand.

Secure transaction

Trustpilot

TrustScore 4.5 | 7,300+ reviews

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Received my product in pristine condition. Great service overall.

1 month ago

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Excellent communication throughout the order process. Product is perfect.

2 weeks ago

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