 The common ¼ inch stereo phone plug. It was originally designed by the Bell Telephone Company around 1880, for use on telephone switch boards. That is why it is called a phone plug. The name has nothing to do with a phonograph. On stereo headphones, the tip is used for the left channel and the ring is the right channel. The ground is a common return path for both the left and right channel conductors.
It takes 2 wires to make a circuit therefore phone lines are discussed in pairs. The label "tip" is usually the positive conductor and the "ring" is usually the negative conductor. They would connect to the phone switch board plugs as shown in the photo above. There are two standard color codes used with phone wires. The oldest is slowly being abandoned in larger cables of more than 6 or 8 conductors, because the new one is much easier to learn and more flexible. The old color code consisted of a very complicated combination of solid colors. Here are the colors for small cables.
And so on, going up to 25 pair and becoming very difficult to remember. In fact the code is so old now that I can't remember it beyond white-blue and can't find it in any of my catalogues. (Note) Jim Stettler wrote me in November of 2001 with the following comments. I'm not sure whether Jim was referring to the Red-Green color code or the newer one but it is most probable the Red-Green one. Thanks for the info Jim. "I used to have a telephone manuel from the late 30's-early 40's that had the standard (current) Color code. The determining factor for using the colors that they did, had to do with the ease of identification along with the availability of dyes for cloth cordage. ie they wanted cheap easy to use dyes that were easy to identify." The newer code, developed in the early 1940s?, is much easier to understand, despite what those telephone closets at the office look like. There are only 10 colors to memorize in a specific order.
Most cables that are not phone company trunk or feeder lines are marked using 2 colors on each wire. If you look at the top 2 wires, pictured below, closely you will notice that one wire is mostly white with a regular band of blue. This is the Tip. The second wire is mostly blue with an regular band of white. This is the ring. Ok so the bands are kind of hard to see. But when seen in longer lengths and twisted, you can make out the colors easier. The wires are twisted to prevent the signal on one pair of wires from "leaking" into the others. When this happens it is called "cross talk" and can be caused by a number of different conditions.
In each pair, the wire with the most color that matches a group color is the tip,
This makes 1 group, or 10 wires, or 5 pair, or 5 phone lines. The second group color is red. Thus...
Using this system you can bundle 50 wires, or 25 pair together with no two wires having the same color. In cables with more than 25 pair, the first group of 50 wires are wrapped with 2 narrow plastic ribbons, one white one blue. The next 50 wires are wrapped with ribbons of white and orange. Under most conditions, this is as many as it goes, interior cables are seldom larger than 50 pair. For some reason, which I have never been able to discover, the next 2 bundles use red and blue and red and orange, however it is very rare to find cables this large except in big buildings wired in the early 1960s. In most newer homes and apartments you will find cables using this newer color code. Normally they only use up to the white-green or maybe to the white-brown pair, giving you 3 or 4 pair. Occasionally homes wired in the 70s had bundles using up to the red-blue pair giving capability of up to 6 phone lines. Sometimes these bundles of wires may be covered with an outer jacket or sheath which may be gray, brown or white. Commonly, houses that were pre-wired with this type of cable, would have the cable pulled in a loop. This simply means the installer pulled the cable out of the center of the box, folded it over, and pulled 2 cables through the walls. When you find this kind of installation, it has the appearance of twice as many wires. Another result is the look of a rats nest when you remove an outlet plate. The reasoning behind this practice was to allow for the possibility of a broken wire in the wall. If a break occurred somewhere in the wall, the home owner wouldn't notice any thing wrong because the signal would go around through the far end of the cable and come back to the phone from the other end. As a matter if interest, most modern computer networks listed as 10-base-T, 100-base-T or even 1,000-base-T (Giga-bit) use the same color codes, although they use different combinations of the conductors than the phone lines. |
