A clue in the numbering of Registered Jack is that the higher the number the more wires is inside. So comparing RJ45 and RJ11 will start with the difference of wires and their capability.
RJ45, because of the number of wires it accommodates is physically larger in size, with 8 wires. This jack is used for computer networking, but can also be used as a telephone line as long as the person handling it is knowledgeable enough and has an experience. It is becoming more popular nowadays, as some houses replace their RJ11 to RJ45 to minimize the amount of visible wires. Other uses include for modem cables, routers, PlayStation and other game devices.
RJ11, on the other hand, is used for telephone and VoIP. It consists of 4 wires, which makes it more slender that RJ45.An advantage of RJ11 is that it can fit it the slots of RJ45, but RJ45 cannot. However, to preserve the quality and integrity of both Jacks, it is better not to do that.
As a conclusion, RJ45 and RJ11 are not interoperable in anyways. The power it can handle differs, to protect the gadget they are used for. One should not be mistaken for the other. If unsure, it is better to consult an expert than to gamble with the products.
Following are key Difference Between RJ45 vs RJ11
| RJ45 | RJ11 | |
| Denote | RJ45 jacks are used in networking, where you connect computers and other network elements to each other. | RJ11 is the cable connector being used in telephone sets. |
| Wires | Eight wires inside | Four wires inside |
| Compatibility | Cannot be use as replacement for RJ11 | Can be use as replacement for RJ45 but it is not advisable. |
