lines at the local telephone exchange, thus making those jacks RJ14 jacks. More often, only two of the wires are connected to the exchange as one telephone line, and the others are unconnected. In that case, the jacks in the house are RJ11. Older houses often have 4-conductor telephone station cable in the walls color coded with Bell System colors: red, green, yellow, black as 2-pairs of 22 AWG (0.33 mm2) solid copper; "line 1" uses the red/green pair and "line 2" uses the yellow/black pair. Inside the walls of the house—between the house's outside junction box and the interior wall jacks—the most common telephone cable in new houses is Category 5 cable—4 pairs of 24 AWG (0.205 mm2) solid copper. Inside large buildings, and in the outdoor cables that run to the telephone company POP, many telephone lines are bundled together in a single cable using the 25-pair color code. References External links Local loop Line Telecommunications infrastructure