Answer Description
RJ-11 supports both a 1 (2 wire) and 2 (4 wire) pair configuration, typically used in telephone systems only 1 pair is traditionally utilized. RJ-45 has 4 pairs (8 wires), Coax has 1 wire, and 4-pin 12V is for power supplies.
Wikipedia
A registered jack (RJ) is a standardized telecommunication network interface for connecting voice and data equipment to a service provided by a local exchange carrier or long distance carrier Registration interfaces were first defined in the Universal Service Ordering Code (USOC) system of the Bell System in the United States for complying with the registration program for customer-supplied telephone equipment mandated by the Federal Communications Commission (FCC) in the 1970s They were subsequently codified in title 47 of the Code of Federal Regulations Part 68The specification includes physical construction, wiring, and signal semantics Accordingly, registered jacks are primarily named by the letters RJ, followed by two digits that express the type
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