Twisted-pair Cable
Several varieties of Ethernet were specifically designed to run over 4-pair copper structured cabling already installed in many locations. ANSI recommends using Category 6 cable for new installations.
| Pin | Pair | Color | telephone | 10BASE-T | 100BASE-TX | 1000BASE-T | PoE mode A | PoE mode B |
|---|---|---|---|---|---|---|---|---|
| 1 | 3 | white/green | - | TX+ | z | bidi | 48V out | - |
| 2 | 3 | green | - | TX- | z | bidi | 48V out | - |
| 3 | 2 | white/orange | - | RX+ | z | bidi | 48V return | - |
| 4 | 1 | blue | ring | - | - | bidi | - | 48V out |
| 5 | 1 | white/blue | tip | - | - | bidi | - | 48V out |
| 6 | 2 | orange | - | RX- | z | bidi | 48V return | - |
| 7 | 4 | white/brown | - | - | - | bidi | - | 48V return |
| 8 | 4 | brown | - | - | - | bidi | - | 48V return |
Combining 10Base-T (or 100BASE-TX) with "IEEE 802.3af mode A" allows a hub to transmit both power and data over only two pairs. This was designed to leave the other two pairs free for analog telephone signals. The pins used in "IEEE 802.3af Mode B" supplies power over the "spare" pairs not used by 10BASE-T and 100BASE-TX.
In a departure from both 10BASE-T and 100BASE-TX, 1000BASE-T uses all four cable pairs for simultaneous transmission in both directions through the use of echo cancellation.
Read more about this topic: Ethernet Physical Layer
Famous quotes containing the word cable:
“To be where little cable cars climb halfway to the stars.”
—Douglass Cross (b. 1920)