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As the photo shows, the pins are wired "straight across", rather than diagonally. This means that it does not work as an Ethernet/8P8C coupler because the transmit pins are mapped to unused pins (for 10/100 Mbit/s at least). Likewise, it doesn't act as a crossover either.

Is it wired wrong? Or is it a special form of a 1000Base-T crossover? Or is it perhaps used to correct the pins from another reversed device...?

Coupler guts Coupler outer

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Maybe for a phone? Where did you find this? – innaM Nov 20 '09 at 21:22
up vote 9 down vote accepted

The color coding of the wires does not comply with computer wiring standards so it isn't CAT5 or CAT6 cabling. The color code is for phone wiring - old style.

All the wires are completely crossed. This is a coupler to connect to RJ-45 phone wires. Probably was used to extend wire for a old office phone.

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Well spotted. So this could be used, for example, for a point-to-point telephone link (assuming the phones had RJ45 cables)? – sblair Nov 20 '09 at 23:15
Assuming you mean to hookup the phones directly to each other? No - much more involved in that - would require a telco simulator. You need "battery" and dial tone and other support functions. Also, this would be for an older phone system, probably, since newer systems do use CAT5/CAT6. – Blackbeagle Nov 20 '09 at 23:24

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