how long should your phone cords be?


handset cord lengths

NOTE: Indicated lengths for handset cords
are the maximum length when s-t-r-e-t-c-h-e-d out—not when they are in their packages.

It's not comfortable or safe to use cords when they're stretched to their maximum, so pick an appropriate length, especially for people who like to walk around.

Some people call us to order cords based on the un-stretched lengths of the cords they have, and even some websites advertise the un-stretched lengths. (People who sell cords should know better.) The chart below should help you figure out what's going on. Lengths are approximate.

It's not comfortable to use cords when they're stretched to their maximum, so pick an appropriate length.

25-foot cord is suitable for walking around a room. It's the most popular length for kitchen wall phones--and the least popular for office phones, because it makes a mess on a desk. Un-stretched, it's about 36 inches long.

12-foot cord is suitable for walking around near a desk or standing near a wall phone. It has become very popular for office phones and is often the right length for a cashier at a restaurant. It's also good if you have a king-size bed. Un-stretched, it's about 17 inches long.

6-foot cord is suitable for sitting at a desk or lying in bed (single, double, or queen-size) when the phone is on the night table. Un-stretched, it's about 12 inches long. It's the standard length handset cord, supplied with most phones.

Custom cords are available. If you prefer 3-feet, 9 feet, 15-1/2 feet or 22 feet just let us know.

line cord lengths

line cord goes from the base of a phone to a phone jack. The standard-length line cord supplied with most phones and other telecom devices is 7 feet long. It's usually long enough to reach a nearby phone jack, if your furniture is arranged the way the architect, or whoever else planned the phone jacks thought the furniture would be arranged.

If your phone or other equipment needs to be located farther away from the phone jack, you can get cords that are 14, 25, 50 or 100 feet long.

You can also get an extension cord to add 25 or 50 feet to a line cord.

Couplers allow you to put two or more cords together when one cord is not long enough.

Be careful when you use a long line cord or an extension cord. Install it where people won't trip over it, animals won't chew on it, and vacuum cleaners won't snag it. You can get a staple gun or hammer-in clips to hold it in place.

Some people want straight telephone handset cords (not coiled), but these cords are nearly impossible to find. We can make one or several for you, in whatever length you need. 

WARNINGCords don't tangle themselves. People tangle cords. Don't think that a straight cord is less likely to get tangled than a coiled cord is. It's not. Furthermore, a tangled straight cord is more likely to break than a tangled coiled cord is.

cord retention channels

Many phone manufacturers now put the handset cord 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.

It's an improvement for the the phone makers, but not for the phone users.

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.

Fortunately, we have cords with extended straight sections that are easy to fit into the grooves or channels in the bottoms of the phones. They're in stock in  colors to match most phones. They'll save you time and avoid frustration.

tips for the business manager or owner

GOOD IDEA: replace all of the cords in your business at one time.

Some years ago, a light bulb manufacturer introduced the concept of "group relamping"—replacing all of the light bulbs in an area, rather than replacing them one-at-a-time as they burned out. Many property managers regarded this as wasteful. It seemed silly to throw out bulbs when they were still working properly. But when the bulb maker pointed out the cost of sending out maintenance people with ladders or hydraulic scissors lifts, and the cost of the interruption to business, it didn't take long for group relamping to become a standard business operation.

There is a parallel with the cost or replacing phone cords.

Unlike light bulbs, phone cords seldom die suddenly, unless they get cut, burned or bitten. Usually they fail gradually over a period of years as they get twisted and stretched and the tabs break off the plugs. Conversations get noisy and are interrupted. People usually tolerate the annoyance for a long time before complaining, often taping up the wounds.

Even the best cords cost only a few dollars each, and we have quantity discounts that can save you a lot of money. If you are a business owner or manager, replace all of the telephone handset cords every few years. How many is a few? That's a good question. Take a look around. It depends on your work environment and your people. Probably somewhere between two and five years. Line cords should probably last ten years or more.


GOOD IDEA: give new employees new phone cords, and maybe new phone handsets, too.

New employees deserve a clean working environment. Get rid of the old ketchup and mustard packs from the desk drawer. Replace the blotter and note pads and chewed-up pencils. And spend a few bucks for a fresh handset cord. Keep some in the supply closet. Also consider a new phone handset, especially if the previous user of the phone was a smoker, sloppy eater, or had bad breath.

GOOD IDEA: color-matched line cords

For many years black phones had black line cords, green phones had green line cords, and even pink phones had pink line cords.


But in around 1970, AT&T realized that they could save millions of dollars if all phones were equipped with neutral silver-gray line cords, regardless of the color of the phones they were attached to.

And since AT&T was a monopoly, customers' complaints could safely be ignored. Later on, when Ma Bell got some competition, most phone manufacturers followed Bell's profitable example since that's what people were used to, and the tradition continues today. Ironically, a $10 kid's phone is more likely to have a color-matched cord than a $400 CEO's phone.

In many cases, particularly if the back of the phone is against a wall, it makes absolutely no difference what color the cord is between the base of the phone and the phone jack, because nobody sees it except when the furniture is moved.

However, if a phone is on a desk away from a wall, and positioned where visitors see the cord when they enter the office, a light gray cord on a black phone sticks out like a sore thumb; and spending a few bucks on a matching cord will restore esthetic harmony.

Your feng shui consultant and interior designer will be very pleased by the improvement. We don't have a dozen colors, but we have enough to make a difference.

BAD IDEA: mismatched handset cords

If a handset cord suddenly fails, you can plug in any color cord to restore vital communications.

But a large number of businesses don't seem to ever get around to replacing the emergency cord with one that's the right color.

There was a very nice Italian restaurant in Scarsdale, New York with a black Panasonic phone that had a white handset cord for at least three years.

The owner would never tolerate a waiter coming to work with one black shoe and one white shoe. But this eyesore—in plain view of every customer—was ignored day after day, year after year; and would only cost a few bucks to correct. Phone cord color doesn't matter in the kitchen, but it does matter up front in a restaurant where people pay $30 for a meal. Inattention to small details like this will get noticed, and shows that management is not managing properly, especially if the problem exists for years. If simple problems are ignored, people begin to wonder what big mistakes are not being corrected.

cord questions & cord answers

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.

CLICK 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: Why do English phone cords have tabs on the ends of the plugs instead of in the middle, like in the United States?

A: It's 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 digital phone?

A: The 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.

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 one.

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 home.

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.

Q: How come I can find 50-foot handset cords in dollar stores but not at phone equipment specialists or electronic stores or this website?

A: 50-foot cords are messy and dangerous. If you think you need one, get another phone for the distant location, or a cordless phone.

Q: 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 here.

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?

A: 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?

A: 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 color?

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: 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.

how to make phone cords last a long time

While we make money when people need new phone cords, we're not greedy. We're perfectly willing to share some tips that will help you get more life out of your phone cords.

  • Believe it or not, some telephone cords are still working fine at age 65—but others don't make it to their first birthday.

  • The longer a phone cord is, the more likely it is to get twisted-up, rolled over by a chair, chewed up by a pet, burnt by a stove, caught in a drawer, or meet some other form of premature death. Don't get anything longer than you need. If you use a phone at your desk, a normal 6-footer should be fine.

  • Lots of people complain that their cords twist up. Well folks, here's the truth: cords don't twist themselves; people twist them.

  • If your cord gets twisted, un-twist it. If you have a really long cord, the best way to untwist it, is to hang it out a window and let gravity help you.

  • Sometimes a cord gets several small twists, where the cord reverses direction. An easy way to fix this is to wrap the cord around a dowel, a stick, a narrow pipe, a broom handle, a toilet plunger, etc., and fix each reversal one at a time.

  • Prevention is better than the cure. If you don't let your cords get twisted, you won't have to untwist them.

  • You can buy cord un-twisters. Some of them are junk that cause static and fall apart in a few months. We have good ones with lifetime guarantees.

  • Some people twist their handset cords until they become a solidified mass and finally break. The hyper-twisting of the coil is usually caused by rotating the handset when switching it from one ear to the other, and then in the same direction when switching back again. Be conscious of what you're doing, and try to rotate your handset in the opposite direction when switching back to the original ear. If you rotate the handset clockwise when switching from left ear to right ear, rotate it counter-clockwise when switching from right ear to left ear. Try it a few times until it becomes natural and automatic. Teach your children, unless they always use a cellphone or cordless.

  • Don't run over your phone cord with the wheels of your desk chair. Try to re-route the cord away from the path of the chair (get a longer cord if necessary). If the cord has to cross a traffic pathway, protect it with CordGuard or other suitable wire covering.

  • Don't stretch your handset cord out to its maximum length. That will put a lot of pressure on the junction between the cord and the plug, and they might separate and you'll have a useless cord.

  • Copy and paste this into an email and send it to all of your staff, or print it and post it where everyone will see it.

WARNING about putting phone cords above ceiling tiles

It can be very tempting to pop out some ceiling tiles to get a long phone cord from one side of a room to the other side, or from one room to another; but it can also be very dangerous.

If the space above a ceiling, but below the floor above it, is a “plenum”—a space used for circulating air for the building's heating and cooling system—you should not just drop in a common PVC-insulated phone cord.

PVC (polyvinyl chloride) is a ubiquitous plastic that’s also been used for toys, phonograph records, food containers, credit cards, house siding, water pipes, shower curtains and 1001 other things.

PVC is useful, plentiful and inexpensive, but it has one serious problem. It can kill you.

When heated to high temperatures in a building fire, PVC releases poisonous gas, forming toxic hydrochloric acid when inhaled by people who work in the building or by firefighters. Once this potential threat was realized, building codes were modified to minimize the potential threat.

PVC-insulated wire either has to be enclosed in protective metal conduit, or PVC is avoided in favor of wire with heat-safe Teflon or similar insulation. Teflon is more expensive than PVC insulation, and a real PITA to work with (it’s hard to strip off and it can cut installers’ fingers), but it’s less expensive than conduit, and doesn’t emit poisonous fumes in a fire.

Ordinary phone cords should not be put above a ceiling if the space between the ceiling and the floor above it is a plenum. If you are unsure, ask the building owner or manager.

Photo shows "Classic Fine Textured" 24" x 24" tiles by Armstrong.

Is it wire or is it cable? What about cords?
And wireless cable?

Just as a ship is a big boat, cable used to mean thick wire.

Computer people have affected telephone vocabulary, and now "cable" seems be be synonymous with "wire," and might eventually replace it.

The name of the British long-distance company, Cable & Wireless, Ltd. comes from the undersea cables that run around the world, and "wireless," the Brit term for radio. Cable & Wireless installed the first telegraph cable between the US and Britain, and tied the British Empire together.

Some cellphone service providers, such as AT&T and Verizon, refer to their services as wireless. That's silly. Some makers of cordless phones call them wireless phones. That's silly, too.

Cordless phones and wireless phones use lots of wires. Just try charging yours without some wire. Even a wireless charger has a wire.

"Wireless Cable" refers to cable-like TV programming sent over-the-air to an antenna on your roof or in your attic. It is NOT satellite TV. Multipoint Multichannel Distribution Service (MMDS) is the technical term for it. Operators broadcast multiple channels of television at microwave frequencies from an antenna located on a tower, tall building, or mountain.

Wire running from the phone company to your place is called the local loop.

The pieces of wire running from a jack to a phone base, and from the base to a handset, are cords.

Wires connecting jacks in patch panels can be called either patch cords or patch cables.

What's the difference between a headset and a handset? And between a handset and a phone? And...and...?

The handset is the part of the phone that goes in your hand, and includes the parts you listen to and talk into. The plastic shell that holds the parts is the handle.

  • If those parts are attached to something that's attached to your head instead of being held in your hand, it would be called a headset, instead of a handset.

  • The important components inside a headset or handset are the transmitter (or microphone) and the receiver (or speaker). What some people call receivers, are really handsets.

  • Some people even call their entire phone a receiver. Yuck. Some companies call them "voice terminals" or "endpoints." That's ridiculous! They're phones, dammit! 

  • Some people, particularly Brits and Aussies, call an entire phone a handset. Double-Yuck (unless it's a cellphone).

  • Headphones have miniature speakers (also known as drivers and transducers and receivers and receiver elements) and are mainly used for listening to music. It's unusual to hear the word "headphone." The word almost always has an "s" at the end. It's a contraction for "pair of headphones," like "pants" is short for a "pair of pants" and "scissors is short for "pair of scissors." Headphones are sometimes called cans.

  • An earphone is a tiny speaker that fits in or on your ear, commonly used for listening to a portable radio.

  • EarPhone® is a tiny ear-mounted speaker with a short microphone boom (sort of a mini headset), made by Jabra for phones.

  • EarSet® is an all-in-the-ear speaker/microphone, also made by Jabra. Similar products from other companies are called ear buds.

  • HeadPHONE is an advertising label that Panasonic uses for some phones that have headset jacks.

about line cords for H-P fax machines

The instruction manual and the Hewlett-Packard website warn that "You must use a cable that has only two copper leads" instead of the much more common four-conductor cord. But people have trouble finding them.


We don't know of any technical reason why a fax, or a phone, or any single-line telecom device that normally requires two conductors, would not work just fine with a four-conductor cord, when the extra wires are not connected to anything; but H-P keeps insisting on it.

H-P tech support said that "sometimes the extra two conductors (wires) can act as an antenna and pick up interference that hurts faxing."

We don't understand why Panasonic, Brother, Sharp, NEC and other brands don't worry about it.

However, if your faxing is going gaflooey, (or kaflooey, or kerflooey) and you’re using a four-conductor line cord, there is a chance that the cord is the source of the trouble. So, if you’ve tried everything else, now try the cord that HP recommends. We have 'em. CLICK

Telephone Biology 101:
Is Jack male or female?

The little plastic tips on the ends of phone cords are plugs. Plugs fit into jacks.

Connectors that are used to carry electricity or electronic signals or data have gender.

Plugs are male. Plug and penis begin with the same letter.

That should be easy to remember, but lots of people get it wrong. Some folks talk about "jacking in," instead of "plugging in." Google shows over 50,000 links for the phrase "jacking in." That's stupid.

Lots of electricians call (female) electrical outlets, "plugs." That's even more stupid.

If you don't understand hardware gender, find someone of the opposite sex, get naked, and look in the mirror. Or study Michelangelo's "Temptation and Fall" on the Sistine Chapel ceiling in Rome.

"Modular" phone plugs are made in three standard sizes. Details are in the next section, below.


all about phone plugs

The little plastic tips on the ends of phone cords and cables are modular plugs. They fit into modular jacks. Despite their male name, jacks are female. Plugs are male.

The word “modular” refers to a phone manufacturing format introduced by AT&T in the 1970s which allowed installers to assemble phones at a customer’s location by selecting specific components that plugged together, instead of needing "hard wiring" with screwdrivers at the factory. This made it easier to replace defective equipment and provided more phone choices with less inventory in the trucks. For example, if an installer had rotary-dial and touch-tone Trimline handsets, and both desk and wall bases, the four phone halves could be assembled to make four different types of complete phones.


Six cord lengths provided even more options.

The modular connector design was also applied to the jacks on walls that phones were plugged into.

Modular plugs are fragile. Repeated plugging and unplugging will cause the tabs to snap off. So will pulling a cord through a snarled mess of wires. If you’re the phone person for your business or home, invest in a supply of plugs and a plug crimper to attach them. If you frequently have to pull cords through tight quarters, get cords with "boots" to protect the tabs.

Modular plugs are made in three basic sizes:

  • The smallest plug, known as 4-position, 2-conductor (or 2 wire), is used for handset cords. A "position" is a groove molded into the plastic that could contain a little bit of gold-plated wire to make contact with wires inside the jack.

  • The middle-size plug is the most common. It has six positions, and two, four, or six wires. It is used for most line cords that connect phones, modems and other devices to phone jacks.

  • The largest common plug, with eight positions and eight wires, is usually used for LANs (Local Area Networks) and sometimes for four-line phones. It is often called an RJ-45, but that designation is inaccurate for LANs.

  • Eight-wire plugs and jacks are also used on some ATT, Lucent and Avaya phone systems. If you are going to re-use jacks previously installed for a Merlin or other phone system that uses the “T568B” wiring scheme, you will either have to re-arrange the wires inside the jack, or connect the circuit that would normally go on the white/orange wire pair, to the white/green pair.


There are other variations that you should be aware of, mostly so you don’t get the wrong thing:

  • Each size plug is made in versions for both solid and stranded wire. Solid wire usually goes inside and on walls. Stranded wire is used for the cords that go from phones to jacks, and for patch cords used for patch panels.

  • There are 6-pin modular plugs with the locking tab at the end instead of the middle, but still on the bottom, made for use with certain products From Digital Equipment Corporation (DEC).

  • In the United Kingdom, the tabs are on the ends of the plugs, not on the bottom.

  • There are also 8-pin “keyed” plugs with an extra bit of plastic on one end to keep them from being inserted into standard jacks.

  • There’s a 10-pin modular plug with an “unofficial” RJ-50 designation used for some special applications. It’s not used for phones.

At least 99% of all phone jacks used with one-line phones could be two-line jacks. In the same jack, if two wires are connected, it's a one-line jack. If four wires are connected, it's a two-liner. (This explanation applies to phone jacks connected directly to phone company dial tone, NOT to jacks within a phone system.) 

The FCC and phone companies have codes to identify how jacks are wired. Registered Jack numbers end with a letter indicating the wiring or mounting method being used.

“RJ” stands for Registered Jack. A single-line jack designed for mounting a wall phone is an RJ-11W. A single-line jack for a table or desk phone is an RJ-11C. Two-line jacks are RJ-14W and RJ-14C. Three-line jacks are RJ-25. If you know that much, you know more than many phone company employees. Four-line jacks are RJ-61. If you know that, you know more than 97% of phone company employees.

“W” stands for Wall. “C” identifies a surface or flush-mounted jack. Apparently only one person knew what the “C” actually stood for, and she died without telling anyone. “S” identifies a single-line jack. “M” identifies a multi-line jack. “X” identifies a complex multi-line or series-type jack. Series jacks are used for alarm dialers and other devices.

Lots of people confuse simple self-contained multi-line phones with the phones used in systems. Multi-line phones used in modern electronic or digital phone systems usually have cords with two or four wires (one or two pairs of wire), regardless of the number of lines on the phone. With today’s technology, one simple pair can handle dozens of phone lines.

If you look at the springy wires inside an ordinary phone jack (one that’s NOT used with a phone system), the two inner wires are used for line #1, and the two outer ones are used for line #2. The flat cords that commonly connect phones to phone jacks follow this same arrangement.

Cords used for three-line phones (probably not made anymore) have two additional conductors for the third line, outside the second pair, for a total of six wires (three pairs). If you look at a cross-section of a six-conductor phone cord, the line circuits could be considered to look like this: 321123. If you plug a single-line phone into a two-line jack, it will work on line #1. If you plug a two-line phone into a three-line jack, it will work on line #1 and line #2.

Four-line cords have two more wires (total of eight wires, in four pairs). Four-line non-system phones can use two two-line cords, or one four-line cord, depending on the phone designer’s preference. Most use two cords.

The diagrams show how jack pins are numbered. By the way, a jack should be installed so the slot for the plug’s tab is at the bottom, and the wire springs are at the top. This way, if any liquid drips into the jack, it won’t cause the pins to short-circuit or corrode. The diagrams were provided by Siemon and 3M. We thank them.

Why are modular phones and cords called "modular?"

In the mid-1970s American phone companies started using phones with parts (i.e., a handset module and a base module) that connected together with plug-in cords, instead of the older "hard-wired" cords that required tools to connect. Modular cords were also introduced to connect from the phone base to a modular jack on a wall. Previous "portable extension phones" used a much larger plug with four prongs. Modular plugs can be attached by machine. The four-prong plugs require human hands for installation, cost much more than modular plugs, and had to be made and stocked in multiple colors. The original Trimline phones used plug-in cords but they were bulkier and costlier than modular cords. Variations of the American modular connector system are used in many countries, and are used for computers, test equipment and even radar detectors.

(above) A: Modern handset with built-in modular jack and its handset cord. B: Ancient hard-wired handset cord with spade lugs. C: Original Trimline five-conductor handset cord. D: Ancient four-hole jack and four-prong plug. E: Ancient "42A" terminal block with hard-wired line cord from phone. (Upper item is the cover.) F: Modern modular "surface jack" with modular line cord from phone. Modular jacks are made in many colors and formats, including surface- and flush-mounting.

(above) We have adapters that will allow you to use a modern modular handset cord with a vintage Trimline phone.

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