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RJ11 cables are similar to RJ45 but with only 6 pins and much smaller connectors as well. RJ-11 cables are used by modems and their heads can support four pins that are very similar to regular phone cables. Therefore, the ports are compatible with the connector type on ordinary telephone cables. Also similar to RJ45 and Ethernet, the RJ11 cable carries electricity to the end point that being a phone or modem device. So it's easy to forget that these are not just data wires but "electrical" wires as well.