Technical professionals have insatiable appetites when it comes to information. Sometimes, though, there are so many new terms and acronyms invading the industry that it’s hard to keep up. With this in mind, we developed a recipe for the second annual EE Reader’s Resource that’s sure to appease the hunger for knowledge.
The glossary is divided into five disciplines: Instrumentation, Data Acquisition, ATE, Communications, and Environmental Test. Since Communications is one of the fastest growing areas in terms of acronyms, this section is divided again into categories focusing on fiber optics, networks/computers, telephony, and radio/wireless.
References
The sources for this information are many, including the following:
Data Acquisition and Control Handbook, Keithley Instruments, 2001, Appendix B Glossary.
Newton. H., Newton’s Telecom Dictionary, 16th edition, Telecom Books, 2000.
www.equipment-reliability.com/glossary.htm
www1.slb.com/semiconductors/testsys/DeFT_terminology.htm
www.testmart.com/advice/glossarytmp.cfm
www.windmill.co.uk/glossary.htm
Instrumentation
Active Edge The rising or falling edge of a signal that will be used to initiate an action.
Autoranging The capability of an instrument to switch among ranges automatically. The ranges usually are in decade steps.
Average Responding A measurement proportional to the average of the absolute values of all input waveforms within a specified frequency range.
AWG Arbitrary Waveform Generator.
Chop Mode A display mode of operation in which small parts of each channel are traced so that more than one waveform can appear on the screen simultaneously.
dB Decibel. A dimensionless unit used to express the ratio of two signal levels; equal to 10 times the common logarithm of the power ratio. dB = 10 log (Power1/Power2); dB = 20 log (Voltage1/Voltage2).
dBc dB relative to the carrier power.
dBm dB referenced to one milliwatt.
DDS Direct Digital Synthesis. A signal-generation technique where the signal is directly synthesized using only digital techniques. This technique generates very precise waveforms, even at low frequencies. Waveforms with correct phase and frequency are obtained immediately after a shift to a new frequency.
Differential Inputs Two inputs, where the measured signal is the difference between them. Any voltage common to both is rejected. Differential inputs can reduce noise picked up by the signal leads.
Drift Slow variation of a performance characteristic such as gain, frequency, or power output; for instance, due to temperature or aging. Usually, drift only is significant when measuring low-level signals (a few millivolts) over long periods of time or in difficult environmental conditions.
ETS Equivalent Time Sampling (also Random Interleaved Sampling). For repetitive signals only, this acquisition mode achieves an apparent very high sampling rate by combining into one record samples taken on many successive, triggered occurrences of the signal.
Four-Terminal Resistance Measurement (also Kelvin Measurement). A measurement where two leads supply current to the unknown resistance and two different leads sense the voltage drop across it.
GPIB General-Purpose Interface Bus, also known as IEEE 488 bus. The GPIB standard is designed to connect several instruments to computers for data acquisition and control.
Ground Loop A current loop created when a signal source and a signal measurement device are grounded at two separate points on a ground bus through which noise currents flow. These currents generate voltage drops between the two ground connections, which cause measurement errors.
Guarding Consists of a guard conductor driven by a low-impedance source surrounding the lead of a high-impedance signal. The guard voltage is kept at the signal potential. The technique reduces leakage errors and decreases response times.
Harmonic Distortion In the output signal of a device, distortion caused by the presence of frequencies not present in the input signal.
IEC International Electrotechnical Commission.
Long-Term Accuracy The limit that accuracy will be equal to or better than during a period of time, typically 90 days or longer. It is expressed as a percentage of a reading plus a number of counts over a specified temperature range.
Maximum Allowable Input The maximum DC plus peak AC value that can be applied between the high and low measuring terminals without damaging the instrument.
Overload Protection A circuit that protects an instrument against excessive current or voltage at the input terminals.
Response Time For a measuring instrument, the time between application of a step input signal and the first indication of its magnitude at a rated amplitude. For a sourcing instrument, this is the time between a programmed change and its appearance at the output terminals.
rms Responding A measurement equal to the rms value of the input signal for all waveforms within the specified frequency range and crest factor limit.
SCPI Standard Commands for Programmable Instrumentation.
Shmoo Plot A graph representing pass/fail test results that will plot pairs of test criteria such as frequency vs. voltage or voltage vs. temperature.
Single-Ended Input An analog input measured with respect to a common ground.
Source Impedance The combination of resistance and reactance that a source presents to the input terminals of a measuring instrument.
Spectral Purity A description of the distortion components of a sine wave at a specified amplitude and load; includes harmonics and spurious components.
Spectrum Analyzer An instrument that displays the frequency spectrum of a signal.
TDR Time-Domain Reflectometer.
THD Total Harmonic Distortion. For a signal, the ratio of the sum of the powers of all harmonic frequencies above the fundamental frequency to the power of the fundamental frequency.
Transconductance The ratio of an incremental change in output current to the incremental change of input voltage causing it when the output voltage is constant.
Trigger Delay The user-settable time or number of events between the trigger event and the acquisition of data.
Trigger Jitter In a digital storage oscilloscope, the short-term variation of the time between a trigger event and the first sample point.
VISA Virtual Instrument Software Architecture. A standard I/O library that provides a single multivendor foundation for instrumentation software.
VNA Vector Network Analyzer.
VXI VMEbus eXtensions for Instrumentation.
VXIplug&play Specifications that enhance VXI hardware compatibility beyond the original scope of the VXIbus standard by providing consistent definition of connectors, interfacing, protocols, drivers, and documentation.
Data Acquisition
Absolute Accuracy A measure of the uncertainty of an instrument reading compared to that of a primary standard traceable to NIST.
Acquisition Rate The rate at which a system acquires data from an external signal. In the case of a multiplexed ADC, it is the aggregate conversion rate for all channels.
ADC Analog-to-Digital Converter.
Aliasing In-band artifacts that cannot be distinguished from the real signal. In a sampled data system, the analog input must be sampled at a rate at least twice the bandwidth of the signal to avoid loss of data (Nyquist Theorem).
Anti-Aliasing Filter A filter passing the lower frequency components of a signal but stopping higher frequencies in either the signal or noise. Anti-aliasing filters are specified according to the sampling rate of the system.
Aperture Delay The delay between the command to start an ADC conversion and the time it actually occurs.
Aperture Jitter Short-term variation in aperture delay.
CMRR Common-Mode Rejection Ratio. The capability of a differential amplifier to determine the difference between the + and – inputs while rejecting the signal common to both.
Cold Junction (also Reference Junction). The junction in a thermocouple held at a stable, known temperature.
Cold Switching Closing the relay contacts before applying the signal and removing the signal before opening the contacts.
Contact Bounce The intermittent opening of relay contacts during closure.
Contact emf Electromotive force across the junction of two dissimilar metals at the same temperature.
Conversion Rate The rate at which sampled analog data is converted to digital data or vice versa.
Crosspoint The intersecting point of a column and row in a relay matrix.
DAC Digital-to-Analog Converter.
DMA Direct Memory Access. A mode in which data is transferred directly between an I/O device and computer memory, bypassing the CPU.
DNL Differential NonLinearity. The maximum deviation of an actual digitized step from the ideal.
Driver Interface software used to control the low-level functionality of boards and instruments. When called by a high-level control program, a driver causes the necessary detailed operations to be performed.
Dry-Circuit Switching Switching below specified levels of voltage and current to minimize any changes in the contact junction.
Dynamic Range The ratio of a specified maximum level of a parameter, such as power, current, voltage, or frequency, to the minimum detectable value of that parameter.
ENOB Effective Number Of Bits. Term used to quantify ADC performance.
Excitation The voltage or current applied to a transducer.
Gain The factor by which an amplifier multiplies an input signal’s amplitude.
Glitch Energy The energy of an unwanted transient. A figure of merit is the integral of the transient voltage with time.
INL Integral NonLinearity. The maximum deviation from the ideal DAC or ADC transfer curve with zero gain and offset error.
Input Impedance The shunt resistance and capacitance (or inductance) as measured at the input terminals, not including effects of input bias or offset currents.
Input Isolation Transformer, electro-optical, or capacitive signal coupling that does not involve a galvanic connection.
Insertion Loss The difference in power output before and after a component is inserted into a circuit. For example, the insertion loss of coaxial cable is a number of dB/ft depending on signal frequency.
Integration Time The time over which an integrating ADC averages the input signal.
Linearity The degree to which a system gain is independent of, for example, amplitude and frequency. In a linear system, if input signals X and Y result in system output S (X) and S (Y) respectively, the input signal aX + bY will result in the output aS (X) + bS (Y), where S is the system transfer function and a and b are scalars.
Monotonicity In a correctly operating DAC, the characteristic of the analog output increasing as the digital-code input to it increases.
MUX Multiplexer. A device that selects multiple inputs into an aggregate signal.
Noise Any unwanted electrical signals contaminating the signal to be measured. This noise may be electronic noise which is an artifact of semiconductor construction techniques and is not reducible. Alternatively, the noise may be caused by environmental factors.
Noise Floor The minimum discernible signal that can be detected by a receiver.
Normal-Mode Rejection Ratio The capability of an instrument to reject interference (usually of line frequency) across its terminals.
Nyquist Theorem The requirement to sample a signal at a rate at least twice its maximum frequency. To get an accurate picture of a waveform, however, a sampling rate of 10 to 20 times the highest frequency is better.
Offset Voltage An error voltage that appears in series with an analog input terminal and is generated by the system’s input circuitry.
Post-Trigger Acquisition Mode A triggering mode in which the data acquisition starts after a trigger event and continues until a number of samples have been acquired.
Pre-Trigger Acquisition Mode A triggering mode in which data acquisition is started before a trigger event occurs and stops relative to the trigger.
Quantization Error The intrinsic uncertainty when digitizing an analog value that is a result of the finite resolution of the conversion process. The level of uncertainty can be reduced by increasing the resolution of the ADC.
Resolution A measure of the smallest change that can be detected in a digital system.
Ringing A transient oscillation in the output that follows a change in input.
RTD Resistance Temperature Device. A sensor that relies on the principle that the resistance of a metal increases with temperature.
S/H Sample and Hold. A circuit that samples an input signal and, upon command, retains or holds the value with minimal droop, usually so it can be accurately digitized.
Scan Typically, a sample of each input channel in turn. The scan will return to the first channel once all the channels have been sampled.
Seebeck Effect The generation of a voltage in a circuit in which there are junctions between dissimilar metals at different temperatures.
Sensitivity A measure of the minimum change in an input signal that an instrument can detect.
Settling Time The time required, after a step change in an input signal, for the output voltage to settle and remain within a specified error band near the final value.
SFDR Spurious-Free Dynamic Range.
SINAD Signal-to-Noise Plus Distortion (ratio).
Slew Rate The maximum rate of change of signal.
SNR Signal-to-Noise Ratio. The ratio of the amplitude of the desired signal to the amplitude of noise signals at a given point in time. The larger the number the better.
Successive Approximation A type of ADC in which the input signal is compared to the output of a DAC. Starting from 0, DAC control bits are sequentially set to 1 starting with the most significant or to 0 if the DAC output exceeds the input signal level.
Thermistor A temperature sensor; a semiconductor that exhibits a large change in resistance as a function of temperature. Most thermistors have a negative temperature coefficient, where resistance decreases as temperature rises.
Thermocouple Two dissimilar metals joined together, making a continuous loop. When one junction has a different temperature from the other, an electromotive force (voltage) is generated.
Timing Jitter The short-term variation of the time period between sample points.
Transducer A device which converts a physical quantity into an electrical signal. Examples include thermocouples and photocells. Most sensors also are transducers.
Voltage-to-Frequency Converter A device that converts an input voltage into a sequence of digital pulses with a frequency proportional to the input voltage.
ATE
Aliasing The most common type of BIST aliasing occurs when two faults have a canceling effect in the signature register.
ATPG Automatic Test Pattern Generation (sometimes Automated Test Program Generation). Tool-based approach to test pattern or program development.
At-Speed Scan Form of scan where testing occurs at the rated frequency of operation. Structure and timing performance can both be verified with this kind of scan test.
BIST Built-In Self-Test.
Boundary Scan Generic term for IEEE 1149.1. It is a methodology allowing complete controllability and observability of the boundary (I/O) pins via a standard interface.
BSDL Boundary Scan Description Language.
Concurrent Test Performing different tests simultaneously.
DFT Design For Test. The practice of adding logic to integrated circuits to facilitate effective testing.
DMA Direct Memory Access. An architecture that allows direct addressability and observability of embedded memories.
DPM The defect level expressed as defective parts per million units.
EDA Electronic Design Automation. The design tools and environment used to develop the logic, draw schematics, and insert scan and BIST for a new chip design.
Fault Coverage Quality measure for a test or set of tests, based on the percentage of actually detected faults vs. the total number of theoretically detectable faults.
Functional Testing (also known as behavioral testing). IC, board, and system testing strategy that focuses on the expected functionality of the product.
IDDQ Quiescent Supply Current.
LFSR Linear Feedback Shift Register.
LSSD Level Sensitive Scan Design. Type of scan design that uses master/slave latches with different clock phases to isolate each scan node.
MISR Multiple Input Shift Register. LFSRs configured as signature analyzers used on the back end of BIST engines to capture and compress output sequences from a circuit under test.
Parallel Test Testing more than one device simultaneously. By convention, this usually is assumed to be identical tests on identical devices.
PRPG Pseudo-Random Pattern Generator. LFSRs sometimes used on the front end of BIST engines to generate pseudorandom patterns.
Site The logical partitioning of tester resources for each device in a parallel test environment.
SOC System on a Chip. Integration of one or more processor cores, embedded memories, peripheral interfaces, and sometimes mixed-signal circuits onto a single chip to form a complete (or nearly complete) system.
SRSG Shift Register Sequence Generator. A simple PRPG (single output).
STIL Standard Test Interface Language. Supported as an output format by the ATPGs of most EDA toolsets. Because STIL is richer in capabilities than WGL, the industry trend is toward full STIL support.
Structural Testing IC testing strategy that focuses on detecting manufacturing defects. Unlike functional or behavioral testing, defects are targeted directly.
STUMPS Self-Test Using MISR and Parallel SRSG. A common BIST architecture that combines a PRPG (or multiple SRSGs), multiple scan chains, and a MISR.
TAP Test Access Port. It is a four- or optionally five-pin port to enable boundary scan.
WGL Waveform Generation Language. De-facto standard for ATPG and vector generation.
WLBI Wafer-Level Burn-In. A manufacturing technique where a particular product is burned in as full wafers to take advantage of massive parallelism and higher temperature acceleration factors.
Communications
Fiber Optics
Absorption The resultant loss of light due to impurities in the glass of an optical fiber.
Attenuation Coefficient The rate of optical power loss relative to the distance along the fiber.
Cladding A material which has a lower index of refraction than the core of an optical waveguide, which surrounds the waveguide, keeping the light in the core.
DBR Distributed Bragg Reflector. Typically, an integrated structure comprising alternate layers of high and low refractive index materials. Construction and material determine the transmission spectrum.
DFB Distributed Feedback Laser. A type of laser used in fiber-optic transmission systems.
Dispersion The broadening of input pulses along the length of an optical fiber resulting in bandwidth limitations within the fiber.
DWDM Dense Wavelength Division Multiplexing. Fiber-optic data transmission system that multiplexes tens or hundreds of different wavelengths of light.
EDFA Erbium-Doped Fiber Amplifier.
FDDI Fiber Distributed Data Interface. A LAN supporting 100 Mb/s data rates and token-ring access.
FOCIS Fiber-Optic Connector Intermateability Standard.
HFC Hybrid Fiber Coax.
Mode How light travels through a fiber. Single-mode fibers have a very narrow core that supports one transmission path for all light rays. Multimode fibers are larger and allow rays to follow different paths.
OC-1, OC-3, OC-12, 0C-48 Optical carrier signaling rates measured in bits transmitted per second. The basic rate for OC-1 is 51.840Mb/s. All higher levels are direct multiples of OC-1.
- OC-3 155.52-Mb/s Optical-Carrier Industry Standard.
- OC-12 622.08-Mb/s Optical-Carrier Industry Standard.
- OC-48 2.488-Gb/s Optical-Carrier Industry Standard.
- OC-192 9.953-Gb/s Optical Carrier Industry Standard.
OPM Optical Power Meter.
OTDR Optical Time Domain Reflectometer. An instrument that measures optical transmission characteristics by sending short pulses of light down a fiber and then presenting a graphic representation of the backscattered light.
SONET Synchronous Optical Network. An international fiber-optic transmission standard.
VCSEL Vertical Cavity Surface-Emitting Laser.
WDM Wavelength Division Multiplexing. Similar to DWDM, except WDM usually refers to only two or four separate wavelengths of light.
Networks/Computers
AAL ATM Adaptation Layer. Converts voice, video, frame relay, and LAN traffic to 53-B ATM cells via segmentation. It reassembles original data at the receiving end.
ADM Add/Drop Multiplexer.
ADSL Asymmetrical Digital Subscriber Line. Analog and encoded digital data sent over existing telephone wiring for up to 18,000 ft. Downstream (customer-receive) rates are 1.536 Mb/s and higher; upstream is 64 kb/s or faster.
APPN Advanced Peer-to-Peer Networking.
ATM Asynchronous Transfer Mode. A high-speed multiplexing and switching method using fixed-length cells of 53 octets to support multiple types of traffic.
ATU-C ADSL Transceiver Unit—Central Office.
ATU-R ADSL Transceiver Unit—Remote Terminal.
Backbone The major multichannel link in a network, from which smaller links branch.
BERT Bit Error Rate Test.
B-ISDN Broadband ISDN.
Bluetooth A standardized, short-range radio link between information appliances. It promises easy connectivity among computers, peripherals, PDAs, and other devices.
BRA Basic Rate Access.
BRI Basic Rate Interface.
CBR Constant Bit Rate (ATM).
CBS Committed Burst Size (Frame Relay).
CDV Cell Delay Variation (ATM).
CER Cell Error Ratio (ATM).
CES Circuit Emulation Service (ATM).
Checksum The sum of a group of data items sent at the end of the packet transmission. The receiver repeats the summation and requests retransmission if the value differs from that sent.
CLP Cell Loss Priority (ATM).
CLR Cell Loss Ratio (ATM).
CRC Cyclic Redundancy Check. An error-detection scheme that generates parity bits by polynomial encoding of digital signals, appends those parity bits to the digital signal, and uses decoding algorithms that detect errors in the received digital signal.
CSDN Circuit Switched Data Network.
CSMA/CD Carrier Sense Multiple Access/Collision Detection (Ethernet).
DCE Data Circuit-Terminating Equipment or Data Communications Equipment. Part of the RS-232 standard and represents, for example, an instrument or modem attached to a PC.
DLL Dynamic Link Library.
DMT Discrete Multitone Carrier (ADSL).
DOCSIS Data Over Cable Service Interface Specification.
DSR Data Set Ready.
DTE Data Terminal Equipment. Part of the RS-232 standard and represents, for example, a PC.
DTR Data Terminal Ready.
ELFEXT Equal-Level Far-End Crosstalk. Far-end crosstalk normalized by subtracting the attenuation of the disturbing pair from FEXT induced on an adjacent pair.
FEXT Far-End Crosstalk. The crosstalk from a signal sent on one pair measured at the far end on an adjacent pair.
Firewall Protection of a network from unauthorized outside access provided by software and/or hardware.
FR Frame Relay. An interface protocol for statistically multiplexed packet-switched data communications in which variable-sized packets (frames) completely enclose the user packets they transport.
FTP File Transfer Protocol. A standard high-level protocol for transferring files from one computer to another.
HDSL High-Rate Digital Subscriber Line. Similar to ADSL, but uses two pairs to provide T1 1.536 Mb/s symmetrical service over 2.2 miles.
HIPPI High-Performance Parallel Interface.
HTML Hyper Text Markup Language.
HTTP Hypertext Transfer Protocol. In the Worldwide Web, a protocol that facilitates the transfer of hypertext-based files between local and remote systems.
IEEE 488 A communications standard bus adopted by IEEE in 1975 for communications between instruments in an automated test system.
IEEE 1394 (also FireWire). A communications standard and external bus that support plug-and-play, hot plugging, and data transfer rates to 400 Mb/s.
ISDN Integrated Services Digital Network.
ISDN-BA ISDN Basic Access.
ISDN-PA ISDN Primary Access.
LAN Local Area Network. A data communications system connecting devices in the same vicinity. Data is transferred without the use of public communications. Examples are Ethernet and token ring.
LANE LAN Emulation.
LAP Link Access Protocol.
LTE Line Terminating Equipment (ISDN).
MAC Media Access Control.
MAN Metropolitan Area Network. A high-speed network designed to link together sites in a metropolitan or campus area. The IEEE has defined the 802.6 standard for MANs based on the Distributed Queue Dual Bus technology.
NEXT Near-End Crosstalk.
N-ISDN Narrowband ISDN.
NMP Network Management Protocol.
NPSI Network Packet Switching Interface.
NSI Network Service Interface.
NTE Network Terminating Equipment.
OSI-7 Open System Interconnect. A seven-layer model for networking protocols and distributed applications: 1) Physical, 2) Data Link, 3) Network, 4) Transport, 5) Session, 6) Presentation, 7) Application.
PCR Peak Cell Rate (ATM).
Peer-to-Peer Communications Communications between networked devices in which any device can initiate data transfer.
PNNI Private Network-to-Network Interface (ATM).
PoS Packet over Sonet.
PPP Point-to-Point Protocol.
PPSN Public Packet Switched Network.
PRA Primary Rate Access.
Protocol A set of rules used in data communications.
PSDN Packet Switched Data Network.
PSELFEXT Power Sum Equal-Level Far-End Crosstalk.
PVC Permanent Virtual Circuit (Frame Relay, ATM).
RS-232 An EIA standard that defines electrical, mechanical, and functional requirements for a serial interface.
RS-422 An EIA standard that defines a balanced (differential) serial interface.
RS-423 An EIA standard that defines an unbalanced (single-ended) serial interface.
RTS Request To Send (RS-232).
SAAL Signaling ATM Adaptation Layer.
SAR Segmentation and Reassembly (ATM).
SCN Switched Circuit Network.
SDH Synchronous Digital Hierarchy. A system architecture used on most continents other than North America for variable-bandwidth transmission of voice, video, and data at very high speeds.
SDSL Symmetrical DSL.
Signaling The process that exchanges digital information to establish, control, and manage connections in a network.
SLIP Serial Line Internet Protocol.
SNMP Simple Network Management Protocol. The defacto standard network management system for TCP/IP-based networks.
SVCA Automatic Switched Virtual Circuit.
SVCR Remote Switched Virtual Circuit.
TCP/IP Transmission Control Protocol/Internet Protocol. An Internet protocol suite consisting of a transport-level protocol and an Internet diagram protocol.
UBR Unspecified Bit Rate (ATM).
UDP User Datagram Protocol.
USB Universal Serial Bus. A serial bus gradually replacing RS-232 and generally included as standard in new PCs.
VBR Variable Bit Rate.
VC Virtual Channel (SONET, ATM).
VDSL Very High-Speed DSL.
VLAN Virtual Local Area Network.
VoDSL Voice over DSL.
VoFR Voice over Frame Relay.
VoIP Voice over Internet Protocol.
VPC Virtual Path Connection.
VPN Virtual Private Network.
WAN Wide Area Network. A data network spanning a large region.
X.25 The first packet data protocol to be widely implemented for the transfer of information.
XML eXtended Markup Language.
Telephony
AFSK Audio-Frequency Shift Keying.
AMI Alternate Mark Inversion.
ASR Access Service Request.
CCITT Comite Consultatif International Telegraphique et Telephonique (International Consultative Committee on Telephony and Telegraphy).
CCS Common Channel Signaling.
CLEC Competitive Local Exchange Carrier.
CNG Comfort Noise Generator.
CO Central Office.
Codec Coder-Decoder. A circuit that converts analog signals to digital code and vice versa.
CPE Customer Premises Equipment.
CSU Channel Service Unit. A digital channel-terminating device on the customer’s premises that performs line coding, conditioning, and equalization functions.
DAA Data Access Arrangement.
DACS Digital Access Crossconnect System.
DLC Digital Loop Carrier.
DS0 through DS3 Standard telephony industry digital signal formats distinguishable by bit rate.
- DS0 64 kb/s.
- DS1 1.544 Mb/s T1 Interface.
- DS3 44.736 Mb/s T3 Interface.
DSL Digital Subscriber Line.
DSLAM DSL Access Multiplexer.
DTMF Dual Tone MultiFrequency.
EPL Echo Path Loss.
ERL Echo Return Loss.
ES Echo Suppressor.
FSK Frequency Shift Keying. A modulation technique that assigns one tone to a 1 and another tone to a 0.
FT1 Fractional T1.
HDLC High-Level Data Link Control.
IDLC Integrated Digital Loop Carrier (connects telephony to SONET).
ILEC Incumbent Local Exchange Carriers.
ITU International Telecommunications Union.
ITU-T ITU Telecommunications Standards Sector.
LE Local Exchange.
LEC Local Exchange Carrier.
MDSL Medium-Speed Digital Subscriber Line.
Modem Modulator/Demodulator. A device that converts digital data into coded analog signals that can be carried on the local loop and vice versa.
MSU Message Signaling Unit (SS7).
PDH Plesiochronous Digital Hierarchy. Two or more signals not generated from the same timing reference but nominally at the same frequency.
PGS Pair Gain System.
POTS Plain Old Telephone Service.
PSK Phase Shift Keying. A method for transmitting digital data over modems by shifting carrier phase.
PSTN Public Switched Telephone Network.
QAM Quadrature Amplitude Modulation (modems).
QoS Quality of Service.
RBS Robbed Bit Signaling (T1).
SLIC Subscriber Line Integrated Circuit.
SS7 Signaling System Number 7. A complex protocol that governs signaling among devices residing in a digital telephone network.
STP Signaling Transfer Point. A switch handling the signaling messages necessary to set up telephone calls, query external databases for routing and processing information, and dispatch call-handling instructions.
SU Subscriber Units.
T/R Tip/Ring.
TIA Telecommunications Industry Association.
TIMS Transmission Impairment Measurement System.
TTE Telecommunications Terminal Equipment.
V.35 ITU Interface Recommendation, V.35.
ZCS Zero Code Suppression.
Radio/Wireless
AMPS Advanced Mobile Phone Service.
AWGN Additive White Gaussian Noise.
BPSK Binary Phase-Shift Keying.
CDMA Code-Division Multiple Access.
CISPR International Special Committee on Radio Interference.
Crest Factor The ratio of the peak value to the rms value of a waveform.
CTIA Cellular Telecommunications Industry Association.
DECT Digital Enhanced Cordless Telecommunications.
DSSS Direct-Sequence, Spread-Spectrum.
DTX Discontinuous Transmission.
Duplexer Simultaneous two-way transmission in either direction on one transmission line.
EDGE Enhanced Data Rates for GSM Evolution.
ERP Effective Radiated Power.
EVM Error Vector Magnitude.
Far-Field Region The region where the angular field distribution essentially is independent of distance from the source.
FDMA Frequency Division Multiple Access.
FEC Forward Error Control.
FHSS Frequency-Hopping, Spread Spectrum.
FWA Fixed Wireless Access.
GFSK Gaussian Frequency Shift Keying.
GPRS General Packet Radio Service.
GSM Global System for Mobile Communications (formerly Groupe Speciale Mobile).
HSCSD High-Speed Circuit Switched Data (higher speed GSM).
I/Q In-Phase/Quadrature.
ITU-R ITU Radio Communications Sector.
Modulation A method to code information on the carrier frequency. Techniques include amplitude, phase, or frequency modulation.
MPE Maximum Permissive Exposure.
NADC North American Digital Cellular.
PCS Personal Communications Services.
Phase Noise Short-term, random phase variations of signal.
PPM Pulse-Position Modulation.
PRBS Pseudo-Random Bit Sequence.
QPSK Quaternary Phase Shift Keying.
Return Loss The reflection coefficient of a mismatch expressed in decibels.
TDM Time-Division Multiplexing.
TDMA Time-Division Multiple Access.
TETRA Trans European Trunked Radio.
UMTS Universal Mobile Telecommunications System.
VSWR Voltage Standing Wave Ratio.
WAP Wireless Application Protocol.
WCDMA Wideband Code Division Multiple Access.
WLAN Wireless LAN.
Environmental Test
Accelerated Life Testing Subjecting products to stress levels much higher than those anticipated in the field. The purpose is to identify failure-prone, marginal elements by causing them to fail. Those elements are strengthened, and tests are continued at higher levels.
Accelerated Stress Testing A production activity. The intent is to precipitate hidden or latent failures caused by poor workmanship by subjecting products to specified stress levels.
Accelerometer A sensor or transducer or pickup for converting acceleration to an electrical signal. Two common types are piezoresistive and piezoelectric.
Burn-In Operating a product, often at constant elevated temperature, to accelerate the aging process.
Coherence A measure of the similarity of vibration at two locations, giving insight into possible cause-and-effect relations.
Compliance The reciprocal of stiffness; i.e., displacement divided by force.
Damping Dissipation of oscillatory or vibratory energy with motion or time. Critical damping provides the most rapid response to a step function without overshoot.
Degrees of Freedom The total number of directions of motion on a structure, including vertical, fore-and-aft, left-and-right, roll, pitch, and yaw.
Design Limit The operational limit of a product beyond which it is not required to function properly.
Deterministic Vibration A vibration whose instantaneous value at any future time can be predicted by an exact mathematical expression. Sinusoidal vibration is the classic example.
DSA Dynamic Signal Analyzer. Vibration analyzer using digital signal processing and the FFT to display vibration frequency components. It also may display the time domain and the phase spectrum.
ESS Environmental Stress Screening. A production process in which 100% of produced units are subjected to stresses more severe than anticipated in service. The object is to precipitate latent defects into recognizable failures.
Environmental Testing Subjecting a sample of products to a simulation of anticipated storage, transport, and service environments such as vibration, shock, temperature, altitude, or humidity.
FFT Fast Fourier Transform. A computational procedure that produces a frequency-domain signal representation from time-domain signal samples.
FMEA Failure Mode and Effects Analysis. A procedure by which each potential failure mode of a system is analyzed to determine the effects on the system and classify each potential failure mode according to its severity.
Forcing Frequency The frequency at which a shaker vibrates.
g The acceleration produced by earth’s gravity. The value for 1 gravitational unit is 9.80665 m/s2 or 32.1739 ft/s2.
HALT Highly Accelerated Life Test. See Accelerated Life Test.
Hard Failure Failure of a product under test that does not revert to correct operation when the test stresses are reduced.
HASS Highly Accelerated Stress Screening. See ESS.
Impulse The integral of force over a time interval.
Inertance (or Accelerance). The ratio of acceleration to force.
Jerk The rate of change of acceleration with time.
Latent Defect A flaw that is dormant and not immediately apparent yet can result in failure. See Patent Defect.
Life Cycle Testing Subjecting products to stresses similar to those anticipated in actual service while collecting engineering data related to life expectancy, reliability, specification compliance, or product improvements.
LN2 Liquid Nitrogen. Often used to rapidly cool environmental test chambers.
MTBF Mean-Time-Between-Failure. A basic measure of reliability for repairable items; the mean number of life units during which all parts of the item perform within their specified limits.
MTTF Mean-Time-To-Failure. A basic measure of reliability for nonrepairable items; the total number of life units of an item divided by the total number of failures within that population.
Modal Analysis The process of breaking complex structural motion into individual vibration modes; resembles frequency-domain analysis that breaks complex vibration into component frequencies.
Modulus of Elasticity Young’s modulus; the initial slope of the stress vs. strain curve where Hooke’s Law applies before the elastic limit is reached.
Natural Frequency The frequency of an undamped system’s free vibration; also the frequency of any of the normal modes of vibration.
Notch The deliberate reduction of a portion of a test spectrum (random vibration testing).
Order Tracking A special case of FFT analysis applied to variable-speed rotating machines where the sampling frequency of the analyzer is an exact multiple of the machine speed.
Patent Defect A flaw that has failed under test or screen. See Latent Defect.
Pitch Rotation in the plane of forward motion, about the left-right axis.
PSD Power Spectral Density. The power of random vibration intensity in mean-square acceleration per frequency unit, as g2/Hz or m2/s3.
Quadrature Motion Any motion perpendicular to the reference axis. Shakers are supposed to have zero quadrature motion.
Random Vibration Vibration characterized by its normal distribution. Because it is nondeterministic, spectra can only be defined in terms of average power spectral density.
Reliability The probability that equipment will perform for a specified length of time under specified circumstances.
Resonance When the forcing frequency equals the natural frequency.
Seismic Having to do with earth motion, as earthquakes.
Shock Pulse A transmission of kinetic energy into a system in a relatively short interval compared with the system’s natural period. A natural decay of oscillatory motion follows.
Simple Harmonic Motion Periodic vibration that is a sinusoidal function of time.
Soft Failure Failure of a product under test that reverts to correct operation when the test stresses are reduced.
Sound Level The quantity in dB measured by a standardized sound level meter. The reading is 20 log10 of the ratio between a given sound pressure and 20 micropascals.
Stepped Sine Testing Frequency incrementally increased or decreased in steps.
Stiffness The ratio of force (or torque) to deflection.
Swept-Sine Testing Smooth and continuous variation of frequency.
Thermal Cycling Subjecting a product to predetermined temperature changes between hot and cold extremes.
Waterfall Plot A series of spectral maps taken at regular intervals of time. Early maps move down the display followed by later maps, something like the flow of a waterfall.
White Random Vibration Broadband random vibration in which the PSD is constant over a broad frequency range.
Yaw Rotation about the vertical axis.
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December 2001