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GLOSSARY of Printed Circuits

by John Walt Childers, IPC-CID, Founder of Golden Gate Graphics

   SYMBOLS    A    B    C    D    E    F    G    H    I    J    K    L    M    N    O    P    Q    R    S    T    U    V    W    X    Y    Z   

Pronunciation Key

Formerly known as

GLOSSARY of Printed Circuit Design and Manufacturing

This glossary has key terminology in use in PCB design and manufacturing, with a smattering of electronics. The definitions were chosen so that their context would likely apply to reading material encountered by a PCB designer. Therefore, many of these terms will have other meanings not given here. See recommended dictionaries below.

This collection of terms came about as I, a PCB designer, ran across words and acronyms in my field for which meanings were hard to find. As I tracked them down, I made them part of this glossary. If you are a PCB designer, then this glossary could be a good place to start when you find a need to look up the meanings of words related to printed circuits or electronics.

TOP        R

Index to terms on this page:

R   radioteletype   rail   rail-to-rail®   RAR   ratsnest   RCI   reactance  
real estate   RefDes  
reference designator   reference plane   register   registration   Relay Coil Terminals A1 and A2   resistors in parallel   resistors in series   RF  
resolve   revert   RFQ   RFID   ripple   ripple current   rise time   RJ   RMB   RMII   RoHS   route   R-R   RRIO   RPP   RTC  

R — (mechanical drawings) radius

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radioteletype — (RTTY) is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations connected by radio rather than a wired link.

Digital HF radio communications systems

Hellschreiber, a FAX-RTTY hybrid, very old system from the 1930s

SITOR, (SImplex Teletype Over Radio) a commercial RTTY variant with error control (the Radio Amateur version is called AMTOR)

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rail — see voltage rail

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rail-to-rail® — Registered trademark of Nippon Motorola, Ltd. for their op amp designs having maximum input and output levels equal to the power supply voltages. See RRIO. [from online Pro Audio Reference Compiled by Dennis A. Bohn]

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RAR — Roshal ARchive format

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ratsnest — A bunch of straight lines (unrouted connections) between pins which represents graphically the connectivity of a PCB CAD database. [Derived from the pattern of the lines: as they crisscross the board, the lines form a seemingly haphazard and confusing mess similar to a rat's nest.)

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RCI — Relative Cost Index

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reactance — Symbolized by X. Opposition to the flow of alternating current. Capacitive reactance Xc is the opposition offered by capacitors and inductive reactance XL is the opposition offered by a coil or other inductance. Both reactances are measured in ohms.
Reactance varies with frequency. The reactance of a capacitor decreases with increasing frequency, but the reactnce of an inductor increases with frequency. [Graf, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999]

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real estate [PCB Slang] Available area on a PCB to place components and run routes with vias. For typical components, it refers to available area on the external layers, the top and bottom of the board. For routing purposes, it would refer to available area on any and all layers.

Micro vias can be used in routing and embedded components could be used on internal layers to maximize the real estate. Both of these technologies are extremely costly.

Thus we have incite into the origin of the term—land and real estate not only consist of area but also cost money.

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RefDes [Altium Designer]  A field name (column heading) formerly used in Altium Designer to mean Reference Designator. Altium no longer uses this field name, having replaced it with " Designator," which they also use to mean Pin Designator (pin number).

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reference designator — (abbreviation "ref des" or "RefDes") The name of a component on a printed circuit by convention beginning with one or two letters followed by a numeric value. The letter designates the class of component; eg. "Q" is commonly used as a prefix for transistors. Reference designators appear as usually white or yellow epoxy ink (the "silkscreen") on a circuit board. They are placed close to their respective components but not underneath them, so that they are visible on the assembled board. By contrast, on an assembly drawing a reference designator is often placed within the boundaries of a footprint --a very useful technique for eliminating ambiguity on a crowded board where reference designators in the silkscreeen may be near more than one component.

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reference plane —  noun  [PCB Design and Electronics]  The ground plane on which a signal's return travels. By test with adequate instrumentation, this will always be the closest ground plane in the layer stackup to the signal. In some cases, the reference plane could be a power plane.

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register — In printed board manufacture, many terms are borrowed from the subject of printing.   Register has the following specialized printing definition from Macmillan Dictionary for Students :

(noun) proper alignment of various plates, stones, or screens to assure clear and accurate reproduction, as of color.   Examples: in register, off register.

In printed circuit design, the designer gets his photoplot files in register before he views them with his Gerber file viewer.  The board manufacturer produces film from the Gerber files and uses them in register with respect to the panels of material from which he will build the boards.  He is going to want the pads on both sides and on internal layers to be in register before he drills holes in the panel.[ Usage note: The term registration is often used in the printed circuit industry for this sense of the noun register . Register , already being a noun, doesn't need the suffix -tion added to it to make it a noun. You wouldn't say, "Count the money in the cash registration."  This misuse of registration has become so common that it has entered the literature of PCB design and manufacturing.  How illiterate we must sound to professional printers when we say "registration" when we mean "register!"]

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registration — See register.

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Relay Coil Terminals A1 and A2 — These are coil terminals of a relay or contactor. They may or may not have polarity. "(A1 + / A2 -)" is how these are described at

Or "A1(+) and A2(-)" at Is The polarity of terminal A1 and A2 from contactor Tesys Green is A1(+) and A2(-) or can customer connect any polarity in the A1 and A2?

This is the convention—A1 is positive and A2 is negative. If you want to open a can of worms, seach the Internet for discussions on "coil terminal A1 versus A2" or "relay a1 a2 polarity." In some relays, it doesn't matter what polarity to use to hook up the coil. In others, it does. Safe bet is go with the convention.

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resistors in parallel — The total resitance of resistors in parallel is less than the resitance of any of the individual resistors. The overall effect of connecting resistors in parallel is to allow more pathways for the current to flow against any resistance. Because there are more pathways for the current to flow, the total value of the resistance in the circuit is decreased.

in parallel resistors formula

Cited Works:
"Rules for Parallel DC Circuits." Repair and Maintenance Manuals - Integrated Publishing. Integrated Publishing, Inc., 2011. Web. 08 Nov. 2011.
Rules for Parallel DC Circuits.

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resistors in series

Rtotal = R1 + R2 + R3 + ... Rn

Cited Works:
Kuphaldt, Tony R., and Warren Young. "Simple Series Circuits." All About Circuits : Free Electric Circuits Textbooks. Ed. Jason Stark and Dennis Crunkilton., Aug. 2002. Web. 08 Nov. 2011. Chapter 5 - Series And Parallel Circuits.

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RF — Radio Frequency.

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resolve [Version Control Management]  Apache Subversion term meaning "the conflict will be resolved by retaining the file as-is in the working directory." Compare with revert.

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revert [Version Control Management]  Apache Subversion term meaning "the conflict will be resolved by replacing the file in the working directory with the version in the repository." Compare with resolve.

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RFQ — Request For Quotation.

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RFID — Radio Frequency Identification

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  1. That portion of the output voltage of a power supply harmonically related to the input power, and to any internally generated switching frequency.
  2. The wavelike variations in the amplitude response of a filter.
  3. The serial transmission of data; a serial reaction that may be compared to a bucket brigade or a row of falling dominoes.
All three definitions from [Graf, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999] .

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ripple current — The alternating component of a substantially steady current. [Graf, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999]   Example: alternating current, considered noise, that is a residual effect of rectification. The direct current produced by a bridge rectifier is imperfect and the imperfections are called ripple current.

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rise time — the time required for an output voltage of a digital circuit to change from low voltage level (0) to high voltage leve (1), after the change has started. (For more defintions of the term, see [Graf, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999] )

Very short rise times, not high clock speeds, are the primary cause of cross-talk in PCBs. Rise times are charactericstic of the technology being used in a circuit. Gallium Arsenide components can have rise times around 100-picoseconds (millionths of millionths of seconds), 30 to 50 times faster than some CMOS components.

A warning for PCB designers. In today's monolithic IC's, rise times have generally shortened to much less than they typically were before 1990. Many IC's have signals with less than 5 nanoseconds [5000 picoseconds] rise times. Any signal with this speed or faster acts like a transmission line and requires special PCB layout techniques. This means that most of your signal routing should be addressing this phenomenon.

"Due to faster rise times and increasing interconnect lengths, the electrical length of interconnects becomes a significant fraction of the operating wavelength, and transmission line effects must be taken into account," writes Roshan Weerasekera in his 2008 doctoral thesis on System Interconnection Design Trade-offs in Three-Dimensional (3-D) Integrated Circuits. This statement applies in both IC design and PCB design. What this means for PCB designers is they need to be aware that stackups and routing techniques that routinely worked 30 years ago won't always work today.
   If you get a chance to attend a workshop by a digital design guru on high speed PCBs, take it. You need this knowhow more than you might realize. Or read Henry Ott's book Electromagnetic Compatibility Engineering

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RJ Registered Jack

  • RJ11 two-contact 6P2C (6 pins 2 contacts) For one telephone line (6P4C if power on second pair)
  • RJ25 six-contact 6P6C (6 pins 6 contacts) For three telephone lines
  • RJ45 eight-contact 8P8C (8 pins 8 contacts) For four-wire data line (Various configurations: DSX-1, DDS and DS1)

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RMB — Right Mouse Button. Sometimes used as a verb to mean "click the right mouse button."

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RMII — R Media Independent Interface

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RoHS — (ROH-hahs) Pronunciation Key  Restriction of the Use of Certain Hazardous Substances (Waste from Electric and Electronic Equipment). These restrictions are required by the European Council, promulgation of laws and regulations are the responsibility of the European countries individually, and implementation is required of manufacturers of electrical products to be used in Europe. "The RoHS Directive (Directive 2002/95/EC), which was finalized by the

European Parliament and the Council of the European Union on January 27, 2003, bans the placement of new electrical and electronic equipment (EEE) containing lead, cadmium, mercury, hexavalent chromium and both polybrominated biphenyl (PBB) and polybrominated diphenyl ether (PBDE) flame retardants starting July 1, 2006.
Brussels, 20 July 2011 – The ban on heavy metals and other dangerous chemicals in electrical and electronic equipment has now been extended to a much wider range of products, with new rules entering into force tomorrow. European Commission Press Release. Environment: Fewer risks from hazardous substances in electrical and electronic equipment.
See also WEEE.

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  1. noun  A layout or wiring of a connection.
  2. verb  The action of creating such a wiring.

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R-R Rail-to-Rail® (q.V.). See also RRIO

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RRIO — rail-to-rail input & output) A term created to indicate op amps with maximum input and output levels equal to the power supply voltages and to avoid violating the registered term rail-to-rail®.[from online Pro Audio Reference Compiled by Dennis A. Bohn]

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RPP — Reverse Polarity Protection

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RTC — Real Time Clock

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Alphabetizing Method

Terms that begin with a symbol or a digit are placed in the SYMBOLS page. Terms that contain digits within them are alphabetized as if the numeric characters were spelled in English.

Terms with two or more words are alphabetized "dictionary style." They are alphabetized as though the spaces between the terms have been removed.
   If there are other characters in the term, such as a slash (/), dash (-) or plus sign (+), these are treated the same as spaces and ignored for the purpose of alphabetizing.

Example Printed Boards

Click for Examples of PCBs designed by Golden Gate Graphics

References and Dictionaries

Modern Dictionary of Electronics by Rudolf F. Graf

This is the best, most usable dictionary for electronics, because its definitions help you grasp the terms and therefore the subject. Lesser dictionaries define electronics terms with even more difficult technical jargon, leading one into endless"word chains." Not this one.
You can buy the Modern Dictionary of Electronics new or used via the Internet.

Graf, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999.

The Random House Dictionary of the English Language, Unabridged, 2nd Edition

You need a big, comprehensive dictionary. Get this one. Despite being a big dictionary, The Random House has great definitions, quick to grasp.

Although out of print, as of 2022 you could still buy a great used copy online for $40 including shipping or possibly for much less. Two versions are available of the 2nd Edition, Unabridged:

I have no idea what the difference is for the deluxe edition, but there seem to be fewer copies of it available in 2020 than the regular edition. I'm sure they both have the same set of definitions. My copy has both ISBNs listed in the front matter, and it is the regular edition.

Flexner, Stuart Berg, and Leonore Crary Hauck, editors. The Random House Dictionary of the English Language. Unabridged, 2nd Edition, Random House, 1987.

Golden Gate Graphics in an official Altium Service Bureau
Golden Gate Graphics is an official Altium Service Bureau