RJ61
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RJ61 (Registered Jack 61) is a physical interface often used for terminating twisted pair type cables. It is one of the Registered Jacks, and uses an eight position, eight conductor (8P8C) modular connector.
RJ61 specifies the wiring pinout of the connector as follows:
| Pin | Pair | Wire | Color |
|---|---|---|---|
| 1 | 4 | tip |  White/Brown |
| 2 | 3 | tip |  White/Green |
| 3 | 2 | tip |  White/Orange |
| 4 | 1 | ring |  Blue/White |
| 5 | 1 | tip |  White/Blue |
| 6 | 2 | ring |  Orange/White |
| 7 | 3 | ring |  Green/White |
| 8 | 4 | ring |  Brown/White |
This pinout is for multi-line telephone use only; RJ61 is unsuitable for use with Ethernet over twisted pair (10BASE-T, 100BASE-TX and 1000BASE-T) because the pins for pairs 3 and 4 are too widely spaced. This causes excessive crosstalk at the high signaling frequencies used by Ethernet, which uses the pinouts specified in TIA-568A/B instead. The pairings for the middle four pins are the same in all three pinouts, but the pair assignments differ; only pair 1 is the same in all three, and pair 2 is the same only in RJ61 and TIA-568A.
With the advent of structured wiring systems that can be used for either voice or data (Ethernet), the RJ61 pinout is falling into disuse because of its unsuitability for Ethernet. The EIA/TIA-568A/B conventions are instead used for both voice and data.
Note that the flat 8-conductor "silver satin" cable traditionally used with 4-line analog telephones is unsuitable for use with Ethernet, even though both applications use the 8P8C modular connector. Twisted pair cable and the pairings given in TIA-568A/B (which are different from the pairings shown above) must be used with Ethernet. The 8-conductor phone wiring is RJ61. T1 lines use another wiring for the same connector, designated RJ48.
[edit] External links
| USOC registered jacks RJ9 | RJ11 | RJ12 | RJ14 | RJ21 | RJ25 | RJ45 | RJ48 | RJ50 | RJ61 |
