"There is no communication in the telephone business"
Michael N. Marcus, 1986

"The telephone business is notorious for using different words to indicate the same thing, and the same words to indicate different things. The merging of computer and telecom technologies is making it even worse."
Michael N. Marcus, 1996

In this Website we generally use key system, rather than PBX terminology. A key system has multi-line phones with keys that you press to get dial tone on a specific line from the phone company's Central Office (CO). In smaller key systems, incoming calls usually ring at several -- or all -- phones. In bigger key systems, calls usually go to the receptionist or attendant, who will then tell someone that he or she has a call on a particular line, often using the intercom to call one phone, or by making a paging announcement to several people, or throughout a large area. With a PBX ("Private Branch Exchange"), you usually use a single-line phone and have to dial 9 to get dial tone. Incoming calls usually go to a receptionist, attendant or operator, who transfers the call to the appropriate person.

• CO, by the way, is pronounced see-oh. It's not "company" or "co."
• Also by the way, when you see "no" on the display on a Panasonic phone, it means "number."
• KTS is the abbreviation for Key Telephone System, often called just a Key System.
• The heart (or brain) of a KTS is its KSU (Key Service Unit). Some telecom newbies say Key System Unit. Computer guys often call it a Central Processing Unit, or CPU. Old telecom guys call it a switch. Cardiologists call it a heart. Neurosurgeons call it a brain.
• An individual module inside a KSU used to be called a KTU (Key Telephone Unit), but this term is disappearing.
• Our Panasonic phone systems combine features of key systems and PBXs, and can use both multi-line and single-line phones, so they are considered hybrid systems.

It's OK to say dial, even if you make your calls by tapping buttons on a touch-tone pad. Touch-Tone was originally a trademark of AT&T, but they let the trademark lapse. A maker of cheapie phones used Touch-Tone as a brand name in the mid-80's, but they seem to have disappeared. Most phones and phone systems can be switched to produce either touch-tones or dial pulses (clicks), like old rotary dial phones, for use with central offices that don't accept touch-tones. The technical term for touch-tone is DTMF (dual-tone/multi-frequency).

• The actual "dial" on rotary dial phones is called the finger wheel.
• Rotary has another meaning in the phone business -- the feature that lets a caller who dials a busy phone number, to automatically connect through another number. This feature may also called hunting or ISG (Incoming Service Group) or Call Forward On Busy.
• Phone company features such as Call Forwarding, Conference Call, Speed-Dial, Call-Waiting, Re-Dial, Call Return and Caller ID, are often called Custom Calling Services, as distinct from POTS (Plain Old Telephone Service). POT, on the other hand, is not a plain old telephone.

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.
• Wireless Cable refers to cable-like TV programming sent over-the-air to an antenna on your roof or in your attic.
• The term wireless is also used to describe cellular phones and PCS phones and phone services.
• The term cordless is usually reserved for wireless home and business phones that are generally used indoors. Cordless phones actually have more wires than corded phones.
• Fancy and/or expensive cordless phones and cordless phone systems are often labeled "wireless."
• Wire running from the phone company to your place is called the local loop.
• Loop plant includes the local loop, plus all the telephone poles and underground conduit and assorted hardware used to connect them to you.
• Wire running around inside your place is station wire, or station cabling.
• The common phone wire that was used for decades, and now considered inadequate, was called D-station wire. It was also classified as IOW, because it could be used Inside and Outside. Wire designed for inside use only, is IW. Most of this wire had four conductors (with green, red, black and yellow insulation), and was also called quad.
• Some of the oldest wire, with three or four conductors twisted together, but with no outer jacket, is called bridle wire.

Modern wire without a jacket is usually cross-connect wire, and is generally used in short lengths to make connections between two terminal blocks (also called punch-down blocks). The photo shows single-pair cross-connect wire that has been punched-down on a common 66M block. The thicker gray wires visible on the left are station wires, connected to individual phones. A group of punch-down blocks near the main phone system control unit may be called a main distributing frame (MDF). A block or blocks farther away, closer to the phones, is an intermediate distributing frame (IDF).

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Most phone installations now use multi-pair station wiring inside the walls, usually with four twisted pairs. The general description is UTP (unshielded twisted pair). It's a good idea to install more pairs than you think you'll need, for adding more phones and gadgets, and to compensate for damage by plumbers and mice.

• Twisted-pair wire varies in the number of twists per inch. Wire with more twists is better and more expensive. UTP is classified in various levels or categories.
• Computer networks generally use Cat-5 wire, and phone systems Cat-3 or Cat-5.
• Cat-5 wire is capable of higher data transmission speeds, and must be installed properly to avoid loss of speed and data glitches. Special phone jacks and other hardware items are available for use with Cat-5 wire.
• Each phone circuit consists of two wires in a pair. One wire, with positive electrical polarity, is called the tip and is traditionally green within a phone jack, the other is negative, called ring, and is red. The tip and ring terms come from the parts of an old-fashioned telephone switchboard plug.
• Multi-pair phone wire uses an industry-standard color code, to distinguish one pair from the others. Each wire usually has a base color and a contrasting stripe, and the other wire in the pair is the opposite. The first pair of wires usually has a white wire with blue stripes, and a blue wire with white stripes. There are codes for 25 different pairs. When cables have more than 25 pairs, each group of 25 pairs is wrapped with colored nylon thread, in a binder group.

With most phone systems, you need a direct path from the central control unit to each phone. Phone guys call this home-run wiring. Computer guys call it star topography.	Loop-through is a less-expensive wiring scheme, often found in homes, where one piece of wire goes from jack to jack to jack.

A cord used to mean a short, flexible, and perhaps temporary piece of wire -- such as the one between the base of a phone and a jack on the wall. Here, too, computer lingo is taking over. Patch cable is now more common than patch cord.

• When a piece of wire is cut to a specific length and has specific connectors or plugs attached, it is usually called a cord or a cable, as in extension cord, or modem cable.
• A cord/cable/piece of wire that connects a phone to a jack is normally called a line cord or sometimes a base cord or a mounting cord. A standard line cord is 7' long. Other common lengths are 14' and 25'. You may also find 50'.
• The coiled cord between the base of a phone and the handset is usually called a handset cord.

The little plastic tips on the ends of cords and cables are plugs. Plugs fit into jacks. Despite their male name, jacks are female. Plugs are male. If you don't understand this, the next time you're naked, look in the mirror. Modular plugs are made in three standard sizes. The smallest plug, known as 4-position/4-wire, is used for handset cords. The middle-size plug is the most common. It has six positions, and either two, four, or six wires. It is used for most line cords, for connecting phones, modems and other devices to phone jacks. The largest plug, with eight positions and eight wires, is usually used for LANs (Local Area Networks) and sometimes for four-line phones. CLICK for a lot more about wire, jacks & plugs.

• In the computer world, a connector can be male or female. In the phone world, a connector is female. A CPC adapter has one (male) plug and two (female) connectors.
• CPE used to mean customer-provided equipment, or its opposite, company-provided equipment. Now it's customer premises equipment, like a phone or a modem. At least one phone company (SNET) says its customer provisioned equipment.
• People sometimes say they "jack-in" a phone. That's silly. You plug-in a phone.
• Some people -- even electricians -- call wall outlets and wall jacks...plugs. That's stupid. Plugs go on wires, not on walls.
• Even though almost all phone jacks go on the wall, the term wall jack is reserved for jacks that are designed to support a wall phone.
• The mushroom-like pieces on a wall jack that fit into slots on wall phones are mounting studs.

Other jacks include surface jacks (like in the picture at left) that stick out from the wall, and flush jacks that are nearly flat, like an electrical outlet (also called a receptacle).

• Surface jacks are often called baseboard jacks, but in modern houses, the baseboard is often replaced by a small strip of molding that is too small to hold a jack, so the jack goes above the baseboard. Surface jacks are also called biscuit jacks.
• Jacks that connect directly to the phone company have RJ designations. RJ stands for Registered Jack, and refers to FCC-established standards. A single-line jack for a wall phone is an RJ-11W. A two-line jack for a desk phone is an RJ-14C. The RJ designation refers to the way a particular piece of hardware is connected at a particular time -- it is not a part number. An RJ-11C, RJ-14C, and RJ-25C can be physically identical, but differ in the number of phone lines connected to them. Many people call an 8-wire jack used for a phone or a computer network an RJ-45. That's a mistake, because an RJ-45 is a jack used to connect a data terminal to a phone line, but since the same piece of hardware can be used for terminals, networks and phones, any 8-wire jack is commonly called an RJ-45.
• The W in RJ designations stands for wall. Nobody seems to know what the C stands for. There are other suffixes, including X.
• RJ21X is a common phone company demarcation point (demark) for up to 25 lines.

In this Website, we use the term line to refer to an individual two-wire circuit (a pair) between your office or home and the phone company. One pair of wires generally provides service for one phone number.

• There are ways to get more out of a pair of wires, and alternatives to wire.
• A SLCC (pronounced slick, and standing for Subscriber Line Carrier Circuit) is used by phone companies when they need to provide dialtone where there is insufficient wire running through the street. It can provide up to 96 derived lines. The smallest unit can squeeze two calls out of one pair of wires. The line voltage on derived lines is usually much lower than the 48 volts on normal lines, and may confuse some multi-line phones. Hold circuits may not work, and in-use lights may be on even when the phone is hung up.
• A T-1 circuit can provide 24 conversations (or data transmission paths) using two pairs of wire. It is commonly used to connect several offices of one company, or to allow a business to connect directly to a long-distance provider, without passing through the local phone company's facilities. Some phone systems can connect directly to a T-1 line, others use an adapter called a channel bank.
• Fiber-optic cables use very thin strands of glass, instead of copper wire, and can carry a huge number of conversations, as well as data and video.
• Microwave uses extremely high frequency radio transmission to carry voice, data, and video between dish-shaped antennas, and is used by phone companies in private networks. The "M" in MCI, stands for Microwave, which the company used in its early days as an alternative to AT&T long distance service.

In this Website, we use phone to mean an individual telephone instrument.

• In PBX lingo, a line is called a trunk and a phone can be called a line, or an extension. In both key systems and PBXs, phones are often called stations.
• People who have worked in offices for a long time often call a phone line a wire, as in "I'm sorry, but Mr. Witherspoon is on another wire."
• Old phone guys often call phones, sets. A wall phone is a wall set and a desk phone is a desk set and a multi-line phone is a key set.
• You may also hear phones referred to by their traditional model numbers. An old-fashioned rotary-dial desk phone is a 500-set. An ordinary touch-tone phone is a 2500-set.
• Phone company customers used to be called subscribers, and telco (telephone company) old-timers often called phones, subsets.
• Old electromechanical key telephones sometimes were referred to with generic numbers, such as K-10 for a key phone with 10 buttons.
• In Bell-Talk, single-line phones were often called CVs (pronounced "see-vees") and key phones were called KVs (pronounced "kay-vees'). If they went on the wall, they'd be a CVW or KVW.
• CVs were sometimes called C-sets.
• These terms were part of the Bell System USOC (UNIVERSAL SERVICE ORDERING CODE) which  consumer and business customers have seldom encountered since the AT&T breakup in 1983. The code included standardized abbreviations for a huge number of hardware items, and were listed on installation orders. The USOC is now used in the wholesale side of the telecom business, where, for example, a competitive local exchange carrier (CLEC) orders service from a telco for resale to its customers. (Thanks to Ray Keating for his help on this.)
• An installation order for a key system was called a K-Plan, and had a chart that showed the functions of each button on each phone.
• K-Plan is different from K-Plant, which was all the key system equipment and support and distribution facilities owned by a phone company. K-Plant almost became a "place" in the minds of phone guys, as in "Joe's in K-Plant."
• Bell's actual hardware items (jacks, adapters, transformers, etc.) often carried a KS designation.
• KS stood for Kearney System, a parts numbering scheme developed for a Western Electric factory in Kearney, NJ. Even today, some common pieces of telecom hardware are marked with KS numbers.
• You might also find pieces of telecom gear with a ComCode, another Bell/Western Electric part number scheme. One 50-cent part can have a dozen different identifiers.
• Phones are often refurbished after being removed from service, so they will look and work like new for other customers. In the old Bell system, refurbished phones and gadgets were known as C-Stock.
• ATT (later Lucent, and now Avaya) sometimes likes to call its phones voice terminals. I think that's silly and pompous and confusing.
• Some people call phones handsets, which is not very pompous, but is even more confusing.
• The handset is the part of the phone that goes in your hand, and includes the parts you listen to and talk into.
• If those parts were attached to something that attached to your head or your ear 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 and the receiver. What some people call receivers, are really handsets.
• Some people even call their entire phone a receiver. Yuck.

When you hang-up briefly to get dialtone for a new call, or to activate call-waiting or another feature, you flash the hookswitch.

• "Flash" refers to a light on an old-fashioned switchboard that would let the operator know that you need help. The "hookswitch" refers to the actual on-off switch inside the phone that would be activated by hanging up or picking up the handset.
• When you pick up the handset, you go off-hook.
• When you hang up, you go on-hook.  
• "Hanging up" refers to the actual switchhook on old phones, where you would hang the receiver.
• A lot of our current telecom vocabulary is based on the parts of ancient phones, like the candlestick above.
• Some phones have buttons labeled flash and some fax machines have hook buttons.

The switchhook's connected to the hookswitch...and the headbone's connected to the neckbone, and that's alright with me.

                                            Michael N. Marcus

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