Resources   Telephone Wiring: If you are doing your own wiring, you need to know the color codes. The original code was based on the 1/4 inch phone jacks used by switchboard operators. The jacks are still used on microphones and head phones and have a distinctive tip and a ring (the ring is insolated from the tip). To make it easy to remember, the color code for the ring was red. Therefore, Ring=Red Tip=Green (Christmas colors). The color codes changed as more phone lines were added and combined into cables. There are two standards; the older one being the Red/Green standard with Yellow as ground, and later Black was added. Black and yellow originally were used to supply power for lighted dials and later used to supply a second phone line. The present and most common color code standard in Blue, Orange, Green, Brown, Slate. This standard uses a specific color combination for each pair of wires. The pairs are grouped into groups of five, and each group has a color; white, red, black, yellow and violet. One bundle holds 25 pairs. The figure to the right shows only the first group (white).   Ethernet: Ethernet wiring uses the same color codes as the telephone. There is one important difference. Since ethernet communication requires a pair for transmit and another pair for receive, there came a need to cross couple the pairs. In other words, if unit A is connected directly to unit B using an RJ45 connector, then unit A’s transmit pair needs to connect to unit B’s receive pair and vise versa. Therefore, there are two connection standards A and B. see figure on the right. When wiring to a hub or to a router, it is only necessary to stick to one of the two types A or B. I prefer to use type B for all of my cabling. Consistency is key. The only time you would need to make a cable with Type A at one end and type B on the other is if you are connecting two computers without a hub, also known as a null-hub or A/B cable.