High Quality Content by WIKIPEDIA articles! Category 4 is a description of a cable that consists of four unshielded twisted-pair (UTP) wires with a data rate of 16 Mbit/s and performance of up to 20 MHz. It was used in token ring networks, 10BASE-T, 100BASE-T4, and is no longer common or used in new installations. It was quickly superseded by Category 5/5e cable, both of which have 100±15 ohm impedance. Twisted pair cabling is a type of wiring in which two conductors (the forward and return conductors of a single circuit) are twisted together for the purposes of canceling out electromagnetic interference (EMI) from external sources; for instance, electromagnetic radiation from unshielded twisted pair (UTP) cables, and crosstalk between neighboring pairs. It was invented by Alexander Graham Bell and he was granted US patent 244,426 Telephone-circuit for the invention in 1881.

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