RJ11 and RJ12 standards are quite close and look identical to each other.
This is because they both use the same connector six slot. The only difference between these two is in the wiring and the number of strands that are used.
RJ12 is a standard 6P6C wiring. This means that there are also 6 strands, which are cable into the connector.
RJ11 is a standard wiring 6P4C and has four strands connected and the remaining two are no longer used.
RJ11 and RJ12 wiring
Despite the differences, both wiring standards are used for the same purpose, telephone lines; commonly using the center pair. But there are also other applications that make use of the RJ12 standard.
Keyed telephone systems and PBXs may take advantage of the additional two connectors. Because of this, RJ12 is not really very common and only the people who have experience working with large company’s telephone systems are familiar with RJ12 wiring.
RJ11, on the other hand, is relatively very common because it is used in the majority of the phone units and wiring of some telephone companies. This has even developed into the connector itself being popularly referred to as RJ11.
There is really no individual decision whether to choose RJ11 or RJ12 in your connection as this is often dictated by the telephone company that you are subscribed to.
With that said the additional two lines that are made available when using the RJ12 standard can become quite handy in a PBX system where you can add extra lines on your own.
- RJ11 and RJ12 wiring uses the same six slot connector
- RJ11 and RJ12 only differs in the wiring
- RJ12 utilizes all six slots while RJ11 only uses four of the six available slots
- RJ11 and RJ12 are commonly used for telephone systems with RJ12 being used in different configurations
- RJ11 is very common in today’s homes while RJ12 is quite uncommon except in some large companies