Questions are answered by
renowned cordiologist Doctor X.
He is not permitted to reveal his identity
here because of restrictions at his "day job," with a major telecommunications equipment manufacturer.
to email questions to the doctor.
Q: What's the difference between the “RJ9,” “RJ10,”
and “RJ22” modular plugs? I've seen them all described as the plugs used on telephone handset cords.
A: They are all used as designations for four-position/four-conductor (4P4C) plugs for telephone handsets or headsets. But since handsets and headsets do not connect directly to the public telecommunications network, the jacks these plugs fit into have no Registered Jack (RJ) codes, and these numbers are fake, phony, and artificial. They are convenient and commonly used, but no one seems to know who started them, or why there are three of them.
Q. I recently bought a handset cord that was supposed to be 25 feet long, but when I opened up the package, it seemed much shorter. What's the story?
A. Coiled cords, including handset cords, are measured at their maximum un-coiled, stretched-out length. They're actually measured before they're coiled, just like "quarter-pound" burgers are weighed before they're cooked and the fat oozes out.
Q. When I put a new modular plug on a phone cord, does it matter which side of the cord I put the tab on?
A. 93% of the time it doesn't matter, but to be safe, use a pen to make a mark on the cord before you take the old plug
off to indicate the side where the tab goes.
Q. What's the difference between "straight-through" cords and "reversed" cords?
A: Modular line cords are used for two basic applications. One is for patching between patch panels or other data communications gear. When used for data patching, cords should always be wired “straight-through” (pin 1 to pin 1, pin 2 to pin 2, etc.). The second application is for connecting phone equipment to a jack. These cords are usually wired “reversed” (pin 1 to pin 6, pin 2 to pin 5, pin 3 to pin 4, etc.)
Here's how to read a modular cord: Align the plugs side-by-side with the contacts facing you and compare the wire colors from left to right. If the colors appear in the same order on both plugs, the cord is wired “straight-through.” If the colors appear reversed on the second plug (from right
to left), the cord is “reversed.” (diagram from Siemon)
Q: Is it OK to re-use a data network jack for a phone. The jack is wider than we need, but the narrow plug seems to fit in OK.
A: Computer networks generally use 8-pin "RJ45" jacks, while most phones use narrower 4-pin "RJ11" jacks. While the pins will line up, it's possible that the narrower plug will wobble around and not make good contact, or actually damage the jack. It would be better to replace the jack, or use our unique
VersaCord, that has an 8-pin plug on one end and a 4-pin plug on the other.
How come I can find 50-foot handset cords in dollar stores but not at phone equipment specialists or electronic stores or
A: 50-foot cords are
messy and dangerous. If you think you need one, get another phone for the distant location, or a cordless
How come I can find couplers for line cords but not for handset cords?
A: Similar answer to
the last question. We have handset cord couplers, but if a 25-foot handset cord isn't long enough,
it's really best to install another
phone, or use a cordless phone.
Q: Why are the
standard lengths for handset cords 6, 12, and 25 feet, but line cords come 7,
14, and 25 feet?
A: Actually, other lengths have been available, and are available now, but these are the most
common. Supposedly when AT&T planned to start offering modular phones in the 1970s, some vice president asked his wife what length cords she thought were appropriate, and these were her suggestions. It was a "focus group" of one.
Q: Is it OK to use an 8-wire RJ45 data cable with a Merlin phone? The plugs look the same.
A: They'll work OK, but because of the bulky protective "boots" on most data plugs, the phones won't fit
properly on the bases or on wall jacks. It's OK in an emergency, but it's better
to use the right cords. You can get them
Q: I've noticed what I
think is an unfortunate trend among telephone manufacturers to put the handset
jacks on the bottom of the phones instead of on the left side, where they were
for many years. This new location requires users to feed the cord through a
narrow groove, often making tight turns, and it's much more complicated than the
old method of just plugging in the cord. Even if I do it right, the cord often
pops out of the groove. Why did the phone makers make this silly change?
It's an improvement -- for them, but maybe not for you. With the old method, the handset jack had to be supported by clips molded into the side of the phone, and connected to the main circuit board by four wires. With the new method, there are no wires. The pins that make contact with the phone cord's plug extend out the back of the jack and are soldered directly to the printed circuit board within the phone. This saves material, time and money. That's more important than making life easy for you, in most manufacturers' way of thinking.
Q: What's the
difference between a cord, a wire, and a cable?
They're all variations of the same thing: wire.
A cord is made up of many strands of very thin wires so it's very flexible, and
is generally used to connect the base of a phone to a phone jack on a wall, or a
handset to the base. Wire uses thicker strands and is less flexible. It usually
goes inside walls, between phone equipment and phone jacks. It also goes between
phone poles and houses, when it's called "drop wire." Just as a big boat is
called a ship, big wire is called cable. There is no official point when wire
becomes cable, but when it has 25 or more individual pairs of wire inside an
outer jacket, the the whole thing is likely to be called cable. Computer people
like the word "cable" better than "cord." What phone guys call a "patch cord,"
computer guys call a "patch cable."
Q: Why are there so
many variations of colors with the same name, and so many names for the same
A: I guess people just
like to be original or different, but it can certainly be annoying. Many phone cord makers list a color as "cherry red," but some edible cherries are very
bright and others are very dark. AT&T's original red phones were dark red, but
IT&T's were bright red. Northern Telecom's "red" was first dark like AT&T and
later bright like IT&T. There are at least three versions of "ash," and some companies call that color "almond" or "chameleon gray." In 1966, Los Bravos
sang, "Black is black I want my baby
back. It's gray since she went away." In the phone business,
"black" is not necessarily black. Sometimes it's charcoal gray; and black phones
and cords can be either glossy black or flat black.
Q: Why don't they make coiled curly LINE
cords? I think they'd be really convenient because they'd take up less space
when people don't need the extended length.
A: At one time they were made, and perhaps
some company does still make them; but there's not much demand. The main reason
for long line cords today, is so a phone can be located farther away from the
phone jack than was anticipated by the person who originally installed the jack.
For this, the normal straight cord is just fine, because it's usually run along
the wall, behind the furniture. If it was coiled, it would not extend as far,
and would collect more dust and be harder to clean than a straight cord. At one
time, people liked to pace around the room while carrying their heavy phone, so
a coiled line cord would be convenient. Today, phoner-pacers use cordless or
cellular phones. There were two fundamental flaws to the coiled line cord: (1)
They got entangled with the coiled handset cord. (2) Dogs and cats and people
would have twice as many curly cords to mess up. You're lucky you don't have
Q: I have a two-line phone at home that
uses a line cord with four wires inside it, but at work my phone has 12 lines on
it, but its cord has just two wires inside it. Why does my home phone use more
wires for fewer lines?
A: You're very observant, but you only saw
part of the picture. The two-line phone you have at home is completely self
contained, but the phone on your office desk is just one part of a system.
There's a big box full of electronics hanging on a wall somewhere at work that
connects the phone to the line you select when you press a line button. Each
line comes into that big box on a two-wire circuit from the phone company, just
like the two two-wire circuits that go directly into your two-line phone at
Q: How do they make a cord curly?
A: A standard flat cord is coiled around a metal rod. Then several rods are placed on a rack, and the racks are put into an industrial oven and baked for a carefully calculated amount of time at a specific temperature that will hold the coil without damaging the wire.
Q: Why do English phone cords have tabs on
the ends of the plugs instead of in the middle, like in the United States?
part of a strange British compulsion to be different. They drive on the wrong
side of the road. They have funny names for things, like "lift" for "elevator"
and "lorry" for "truck" and "football" for "soccer." They use 220 volts instead
of 110 volts and have a queen instead of a president and they drink warm beer.
Q: What kind of cord should I get for a
same kind of cord that would be used for an analog phone. Although most digital
phones only need one pair (two wires) in their line cords, it is common industry
practice to use two-pair (four wire) cords. The handset cords have four wires
just like analog phones.
Q: How long do phone cords last?
A: While there are certainly great
variations in manufacturers' quality, the biggest factor in cord life has to be
the habits of the people who use them. People who stretch, twist, chew on, run
over their cords with their chairs, close them in desk drawers or file cabinets, and dangle their cords over the burners on
stoves can kill the best cord in the world in a few months. On the other hand, a
gentle person might make a crappy cord last for a few years. All cords
deteriorate gradually. If you are a business
owner or manager, you should probably replace all of the telephone handset cords
somewhere between two and five years. Line cords should probably last ten years
or more. I've seen residential phones with cords that are 50 years old and are
still just fine.
to email questions to Dr. "X."