RJ11 and RJ45 connectors are ubiquitous and critical to modern communications and data infrastructure, with millions of them being sold and integrated into new equipment every year. we field a great many questions about them, among them being whether any given connector has a voltage or current rating available. These devices rarely list either specification; why is this?
In the case of telecom and data transmission devices like these, both RJ11, RJ45, and most other ‘RJ’ standards are tightly controlled in terms of the amount of voltage and current the system is allowed to utilize. The connectors made to meet these standards assume these values are the ones the end user will use, and so they do not design or test these connectors to withstand higher voltages or current. Such design/testing would significantly increase the cost of these devices for no real benefit in their intended application, and a manufacturer cannot really design or test a connector for unintended uses. If you need a listed current or voltage spec for these devices, you can look up those specs for the relevant standard being used and record those values for your project.
One exception is known as Power Over Ethernet, which pairs a degree of power transmission capability with conventional RJ45 Ethernet cabling. Usually this is done to simplify system implementation and wiring, reducing the number of cables that need to be run and the number of ports that need to be included in the client-end device. For more information on Power Over Ethernet, you can check out our primer on it here: Power over Ethernet Standards and Capability