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Why does RJ45 have 8 wires?
Knowledge Base + 2024.01.12

The RJ45 connector, commonly used for Ethernet networking, has 8 wires because it follows the TIA/EIA-568-B wiring standard, which specifies the arrangement of conductors within the connector. These 8 wires are organized into four pairs, and each pair serves a specific purpose in transmitting and receiving data.

The TIA/EIA-568-B standard defines the pinout arrangement for the RJ45 connector as follows:

  1. Pair 1 (Pins 1 and 2): Transmit Data + (TD+)

  2. Pair 2 (Pins 3 and 6): Transmit Data - (TD-)

  3. Pair 3 (Pins 4 and 5): Receive Data + (RD+)

  4. Pair 4 (Pins 7 and 8): Receive Data - (RD-)

The use of four pairs of wires allows for the implementation of differential signaling, which enhances the reliability and performance of data transmission. In Ethernet networking, these pairs are used for full-duplex communication, where data can be transmitted and received simultaneously.

Additionally, having multiple pairs provides the flexibility to support different networking standards and applications. For example, Gigabit Ethernet uses all four pairs for simultaneous bidirectional communication, while older standards like 10/100Base-T only use two pairs.

In summary, the RJ45 connector has 8 wires organized into four pairs to support the requirements of Ethernet networking, allowing for efficient and reliable data transmission.