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Telco Colors

Four Pair

			10BASE-T 100BASE-TX
Pin	T568B	T568A	MDI	MDI-X	100BASE-T4	1000BASE-T	Token Ring
1	White / Orange	White / Green	TX+	RX+	TX_D1+	BI_DA+
2	Orange	Green	TX-	RX-	TX_D1-	BI_DA-
3	White / Green	White / Orange	RX+	TX+	RX_D2+	BI_DB+	TD-
4	Blue	Blue			BI_D3+	BI_DC+	RD+
5	White / Blue	White / Blue			BI_D3-	BI_DC-	RD-
6	Green	Orange	RX-	TX-	RX_D2-	BI_DB-	TD+
7	White / Brown	White / Brown			BI_D4+	BI_DD+
8	Brown	Brown			BI_D4-	BI_DD-

Pins are numbered 1–8 from left to right across the back of the plug with the tab down, or looking straight into a jack with the tab down.

Most commercial installs use T568B, while government and homes tend towards T568A. Use one of each to make a crossover cable.

Use Category 3 or better cable for 10BASE-T and 100BASE-T4, Category 5 or better for 100BASE-TX, and Category 5e for 1000BASE-T.

The signals carried on each wire are as follows. For 10BASE-T and 100BASE-TX, computers use the MDI pinout show in the table below, while switches and hubs use MDI-X, which reverses TX and RX.

Twenty Five Pair

Primary colors are: White, Red, Black, Yellow, Violet.

Secondary colors are: Blue, Orange, Green, Brown, Slate.

So, the first pair is white and blue, the second is white and orange, and the twenty-fifth pair is slate and violet. Tip (ground) is predominantly the primary color, and ring is predominantly the secondary color.

If there are more than 25 pairs, up to 24 bundles are wrapped into a binder group with a color coded thread (repeating the above color code except for violet/slate). If this isn’t enough, they are wrapped into super groups of 600 pairs using the color code: White, Red, Black Yellow, Violet, Blue, Orange, Green, Brown, Slate. I have no idea if there’s a system for more then six thousand pairs.

Some Pair

The old solid color system. First: green is tip, red is ring. Second: black is tip, yellow is ring. Third: white is tip, blue is ring.

Other Pinouts

	ISDN BRI		Serial
Pin	TE	NT	Cisco	Cyclades
1			RTS	CTS
2			DTR	DSR
3	TX+	RX+	TxD	RxD
4	RX+	TX+	GND	GND
5	RX-	TX-	GND	GND
6	TX-	RX-	RxD	TxD
7			DSR	DTR
8			CTS	RTS

Note that a rollover cable acts as a null modem for either serial pinout. Sun is the same as Cisco.