1996 Telecommunications Act
Legislation designed to spur competition among wireless and wireline carriers. Signed into law by President Clinton in February 1996.

2G
Abbreviation for second generation. An improvement over the original design.

3G
Abbreviation for third generation. The next generation of wireless technology beyond personal communications services. The new standard promises to offer increased capacity and high-speed data applications up to 2 megabits.

802.11
The Institute of Electrical and Electronics Engineers standard for wireless local area network interoperability.

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A/D
Abbreviation for analog-to-digital.

Absolute maximum rating
Maximum rated voltage value assuring the normal operation of a crystal oscillator. Exceeding this value may result in a decrease in the reliability of a crystal oscillator.

AC
Abbreviation for alternating current. In electricity, alternating current (AC) occurs when charge carriers in a conductor or semiconductor periodically reverse their direction of movement. Household utility current in most countries is AC with a frequency of 60 hertz (60 complete cycles per second), although in some countries it is 50 Hz.

ACPR
Abbreviation for adjacent-channel power ratio.

Active satellite
A functioning satellite that receives and transmits or retransmits radio communication signals to or from a base station.

Activity
A term associated with the resistance of a crystal unit. A crystal unit with low resistance is said to have good activity while a crystal unit with high resistance is said to have bad activity.

Activity Dip
Used to describe an abrupt increase in the resistance and a perturbation in the frequency of a crystal unit, followed by an equally abrupt return to the prior values.

Adaptive array antennas
A type of advanced smart antenna technology that continually monitors a received signal and dynamically adapts signal patterns to optimize wireless system performance.

ADC
Abbreviation for analog-to-digital converter. A device that converts an analog signal to a digital signal that represents equivalent information.

AFC
Abbreviation for automatic frequency control.

AGC
Abbreviation for automatic gain control. A process or means by which gain is automatically adjusted in a specified manner as a function of a specified parameter, such as received signal level.

Aging
A systematic change in frequency and/or resistance with the passage of time due to internal changes in the crystal and/or oscillator. Aging is typically expressed as a maximum value in parts per million per year [ppm/year]. The rate of aging is typically greatest during the first 30 to 60 days after which time the aging rate decreases. Aging is affected by adsorption and desorption of contamination on the surfaces of the quartz, stress relief of the mounting and bonding structures, material outgassing, and seal integrity.

AGL
Measurement of tower height above the ground. Also referred to as tower height.

AM
Abbreviation for amplitude modulation. A type of transmission used in either the standard radio broadcast band at 535-1005 KHz, short-wave broadcasting and in some private radio services such as citizens band (CB) and aviation.

Amateur radio operator (HAM)
A noncommercial, private radio operator. There are six classes of amateur radio licenses that can be earned after passing FCC-administered examinations.

AMPS
Abbreviation for advanced mobile phone system. AMPS is a standard system for analog signal cellular telephone service in the United States and is also used in other countries. It is based on the initial electromagnetic radiation spectrum allocation for cellular service by the Federal Communications Commission (FCC) in 1970. Introduced by AT&T in 1983, AMPS became and currently still is the most widely deployed cellular system in the United States.

AMTA
Abbreviation for American Telecommunications Association. A Washington, DC based trade group representing specialized mobile radio operators.

Angle
The angle at which a resonator plate is cut from the quartz stone in relation to the original crystallographic axes. The angle of cut is critical to the performance of the crystal unit, particularly in the area of frequency deviation over a temperature range.

ANSI
Abbreviation for American National Standards Institute. The US standards-setting body. It is a non-governmental agency that develops and publishes standards for "voluntary" use.

Antenna
Any structure or device used to collect or radiate electromagnetic waves. A device that converts radio frequency electrical energy to radiated electromagnetic energy and vice versa; in a transmitting station, the device from which radio waves are emitted.

APCO
Abbreviation for Association of Public-Safety Communications Officials-International. Trade group headquartered in South Daytona, Florida, representing law enforcement, fire, emergency services and other public-safety agency dispatchers and communications employees.

ASIC
Abbreviation for application-specific integrated circuit.

Assigned frequency
The center of the assigned frequency band assigned to a station. The frequency of the center of the radiated bandwidth.

ASK
Abbreviation for amplifier shift keying.

ASP
Abbreviation for application service provider. An ASP is a company that offers access over the Internet to applications and related services that would otherwise have to be located in their own personal or enterprise computers.

AT Strip
An AT-cut crystal in the shape of a rectangular strip. It has a higher ESR than a round AT-cut crystal but is smaller in size, thus allowing smaller crystal packages.

AT cut
The commercial designation for a specifically oriented resonator plate, having desirable and repeatable operating characteristics. A plate cut from a crystal of quartz such that the plate contains the X-axis and makes an angle of about 35 degrees with the optic or Z-axis. The AT-cut crystal is the most popular thickness-shear crystal unit manufactured today. It has excellent temperature and frequency characteristics. This design provides 70 to 80% of all crystal requirements. The frequency vs. temperature curve is a sine with the inflection temperature at ~ +25"C. Preferred for high frequency oscillator control over a wide temperature range for TCXO, VCXO, and Ovenized oscillators. Frequency range is from 500 KHz to 200MHz. Also used for filters. See BT cut.

ATM
Abbreviation for asynchronous transfer mode. A high-speed multiplexing and switching method utilizing fixed-length cells of 53 octets to support multiple types of traffic. Note: ATM, specified in international standards, is asynchronous in the sense that cells carrying user data need not be periodic.

Attenuation values
A decrease in power of a received signal.

Attenuation
The maximum guaranteed reduction in power, ranging outside a specified frequency span. Spurious response attenuation is the minimum acceptable attenuation in the stopband, which allows for unwanted modes in the crystal.

Audio frequency (AF)
Generally in the range 20 Hz to 20 KHz.

AUTELSAF
European regional satellite facilities consortium owned by approximately 40 European countries

Automatic Frequency Control (AFC)
Similar to Automatic Fine Tune (AFT). A circuit that keeps a receiver in tune with the wanted transmission.

Authentication center
Abbreviation AuC. A functional piece of the HLR used to authenticate the user of mobile station equipment.

AVL
Abbreviation for Automatic Vehicle Location. Combining a locations-sensing device (such as a GPS receiver) with a wireless communications link to provide a home office or dispatcher with the location of a vehicle or mobile asset.

AWGN
Abbreviation for additive white gaussian noise. See white noise.

Axis
A direction in a quartz stone. The plural of "axis" is "axes."

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Backhaul
A term used to define the communications link, typically microwave or fiber optical, between a base station and a communications switch or communications network.

Band
The range of frequencies in the same spectrum.

Bandpass limiter
A device that imposes hard limiting on a signal and contains a filter that suppresses the unwanted products of the limiting process.

Bandpass filter
A passive electronic circuit that allows a narrow range of frequencies to pass through the device while blocking or attenuating higher and lower frequencies. Crystals are used for narrow bandpass filters.

Bandwidth
The total range of frequencies required to transmit a radio signal without undue distortion. The required bandwidth of a radio signal is determined by the amount of information in the signal being sent.

Bar (Quartz)
Term used to refer to a quartz stone that has been machined on at least two sides.

Barkhausen criteria
States that for oscillation to occur the product of the gains around a loop must be equal to or greater than unity and that the sum of the phase shifts around the loop must be a multiple of 360°.

Base
The lower portion of a crystal holder. The base incorporates a resonator mounting structure and leads or pins to connect the device to an external circuit. See holder.

Base plating
The process of plating electrodes on to a crystal wafer.

Base station
Fixed radio station used by RCCs (radio common carrier) to send, receive and transport signals. See land mobile.

Base station controller (BSC)
The BSC is a device charged with managing radio frequency resources and radio frequency transmission for a group of basic trading areas (BTSs).

Base station subsystem (BSS)
A device charged with managing radio frequency resources and radio frequency transmission for a group of basic trading areas (BTAs).

Base transceiver station (BTS)
A device utilized to transmit radio frequency over the air interface.

Baseband signaling
Transmission of a digital or analog signal at its original frequencies. The signal is in its original form, not changed by modulation.

Baseband
The original band of frequencies produced by a transducer, such as a microphone, telegraph key, or other signal-initiating device, prior to initial modulation.

Bent pipe technology
Satellite technology to transmit calls from one point on Earth to a satellite and back down to another point.

BER
Abbreviation for bit error rate. The number of erroneous bits divided by the total number of bits transmitted, received, or processed over some stipulated period.
Note 1: Examples of bit error ratio are (a) transmission BER, i.e., the number of erroneous bits received divided by the total number of bits transmitted; and (b) information BER, i.e., the number of erroneous decoded (corrected) bits divided by the total number of decoded (corrected) bits.
Note 2: The BER is usually expressed as a coefficient and a power of 10; for example, 2.5 erroneous bits out of 100,000 bits transmitted would be 2.5 out of 105 or 2.5 10-5.

Bevel
A modification to one or both of the major faces of a resonator plate in which the face is altered to have a partially spherical configuration. See contour.

Bi-directional antenna
Antenna that radiates most of its power in two directions.

Bird
A colloquial expression used to refer to a communications satellite.

Blank
A quartz resonator plate. Also known as a wafer, a plate, or a resonator. A round or rectangular quartz crystal that has been lapped to produce very parallel major surfaces and has minor surfaces machined to the final dimensions required to build the desired resonator. A machined disk of single crystal quartz.

Booster
A television or FM broadcast station, operating at relatively low power that receives a distant input signal, amplifies it, and retransmits it on the same channel.

BPSK
Abbreviation for binary phase shift keying.

Broadband
A general term used to describe wide bandwidth equipment or systems which can deliver multiple channels and services like voice, data, video; i.e., a circuit that operates at a frequency of 20KHz or greater. Also called wideband.

Broadcast
Delivery of a transmission to two or more stations at the same time, such as over a bus type local network or by satellite.

BT cut
The commercial designation for a specifically oriented resonator plate, having well known and repeatable characteristics. See AT cut.

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C Band
Certain high-frequency radio frequency bands between 3,900 and 6,545 MHz used by communications satellites in the fixed satellite service.

C.I.
The abbreviation for crystal impedance, sometimes used in place of the word resistance.

C.I.M.
Abbreviation for crystal impedance meter. See test set.

C0
Abbreviation for shunt capacitance.

C1
The abbreviation for motional capacitance. Motional capacitance is also often abbreviated as Cm.

Calibrated
The process of plating a crystal to the finished frequency.

Calibration
The setting tolerance is the maximum allowable deviation from the nominal frequency at 25°C. It is normally specified in parts per million (ppm).

Calibration Accuracy
See frequency tolerance.

Can
The upper portion, or cover, of a crystal holder. See cover and holder.

Capacitance ratio
In applications (i.e. VCXO) where variations in the crystal parallel resonant frequency are desired, the capacitive ratio (r) may be specified. This ratio is an indicator of the change in a parallel load resonant frequency as a direct result of a given change in crystal load capacitance. Because the value of this ratio has physical limitations when it is realized in a quartz crystal design, please consult the factory for product specifications. r = C0/C1

Capacitance
The property exhibited by two conductors separated by a dielectric whereby an electric charge becomes stored between the conductors. Capacitance is measured in "farads" and is identified by the letter "C."

Capacitor
A passive electronic circuit component consisting, in its simplest form, of two metal electrodes separated by a dielectric.

Capacity
The average amount of traffic that a circuit or circuit group can handle.

Carrier frequency
The nominal frequency of a carrier wave.

CCRR
Abbreviation for co-channel rejection ratio.

CDMA
Abbreviation for code-division multiple access. A coding scheme, used as a modulation technique, in which multiple channels are independently coded for transmission over a single wideband channel.
Note 1: In some communication systems, CDMA is used as an access method that permits carriers from different stations to use the same transmission equipment by using a wider bandwidth than the individual carriers. On reception, each carrier can be distinguished from the others by means of a specific modulation code, thereby allowing for the reception of signals that were originally overlapping in frequency and time. Thus, several transmissions can occur simultaneously within the same bandwidth, with the mutual interference reduced by the degree of orthogonality of the unique codes used in each transmission.
Note 2: CDMA permits a more uniform distribution of energy in the emitted bandwidth.

CDPD
Abbreviation for cellular digital packet data. CDPD is a specification for supporting wireless access to the Internet and other public packet-switched networks.

Cellemetry
Brand name for BellSouth Cellular Corp.'s telemetry service, which uses the cellular network to carry data messaging used for remote services such as utility meter reading, vending machine status and vehicle or trailer tracking.

Center Frequency or Nominal Frequency
The midpoint in the passband. The specified reference frequency of the crystal and is typically specified in megahertz (MHz) or kilohertz (kHz).

Central Processing Unit System (CPU)
The portion of a computer that includes circuits controlling the interpretation and execution of instructions and also the portion that executes programmed instructions, performs arithmetic and logical operations on data, and controls input / output functions.

Channel
A single path, either RF or voice, for transmitting electrical signals between a sending point and receiving point. Channels are often measured in terms of the amount of spectrum they occupy (bandwidth) measured in Hertz.

Channel elements
The frequency determining device in communications equipment. (i.e. oscillator, TCXO, and/or VCXO).

Channel spacing
The difference in frequency between successive radio or television channels.

Chemical etching process
Cleaning quartz resonators by removing some of the surface.

Circuit
Physical connection of channels, conductors and equipment required to provide a complete communications pathway.

Clear channel
A clear channel protects stations designated as Class A stations from objectionable interference within their primary and secondary
service areas. To provide this wide service area, Class A stations operate within a power range of 10 to 50 kilowatts.

Clock
A device providing signals used in a transmission system to control the timing of certain functions such as the duration of signal elements or the sampling rate. A device that generates periodic, accurately spaced signals used for such purposes as timing, regulation of the operations of a processor, or generation of interrupts.

Clock rate
The rate at which a clock issues timing pulses.

Cm
Abbreviation for motional capacitance.

Cold Weld
Welding in which a molecular bond is obtained by a cold flow of metal under extremely high pressures, without heat; widely used for sealing transistors and quartz crystal holders.

Co-location
Placement of multiple antennas at a common physical site to reduce environmental impact and real estate costs and speed zoning approvals and network deployment. Co-location can be affected by competitive and interference factors.

Colpitts oscillator
An oscillator in which a parallel-tuned tank circuit has two voltage-dividing capacitors in series, with their common connection going to the cathode in the electron-tube version and the emitter circuit in the transistor version.

Common-Mode Rejection Ratio (CMRR)
The ratio of the common-mode interference voltage at the input of a circuit, to the corresponding interference voltage at the output.

Communications satellite
A satellite that is used to relay telecommunications information.

Complementary Metal-Oxide Semiconductor (CMOS)
The semiconductor technology used in the transistors that are manufactured into most of today's computer microchips.

COMSAT
Abbreviation for Communications Satellite Corporation. Corporations, chartered by Congress, as an exclusive provider of international telecommunications satellite channels to the US COMSAT also represents the US in INTELSAT.

Conductor
A material that easily conducts an electric current because some electrons in the material are free to move.

Contour
A modification to one or both of the major faces of a resonator plate in which the face is altered to have a completely spherical configuration. See bevel.

Coupled mode
An unwanted mode that becomes energized at the same frequency as the desired mode, thereby draining energy from the desired mode.

Cover
The upper portion of a crystal holder. See holder.

Covered SMR
A subset of specialized mobile radio operators subject to a particular set of regulations.

Crystal
A generic term used in place of the more complete expression piezoelectric quartz crystal unit. A homogenous solid formed by a repeating, three-dimensional pattern of atoms, ions, or molecules and having fixed distances between constituent parts. Usually a mineral, especially a transparent form of quartz, having a crystalline structure, often characterized by external planar faces.

Crystal blanks
Round or square wafers of quartz crystals.

Crystal calibration
See calibrated.

Crystal cut
The orientation of the crystal element with respect to crystallographic axis of the crystal.

Crystal element
Piezoelectric material cut to a given geometric shape, size and orientation with respect to the crystallographic axis of the crystal.

Crystal enclosure
The enclosure protecting the crystal vibrator(s) and mounting system.

Crystal Equivalent Circuit
A crystal device consists of a quartz resonator with metal plating. This plating, as shown in Figure 3, is located on both sides of the crystal and is connected to insulated leads on the crystal package. The device exhibits a piezoelectric response between the two crystal electrodes as expressed in the equivalent circuit shown in Figure 4.

Figure 3

Figure 4

Crystal filter
An electric wave filter employing pies-electric crystals for its reactive elements. In general, filters can be provided in a number of differing topologies, including bandpass, band reject or notch, low pass, and high pass.

Crystal oscillator
An oscillator in which the frequency is controlled by a piezoelectric crystal. A crystal oscillator may require controlled temperature because its operating frequency is a function of temperature. Types of crystal oscillators include voltage-controlled crystal oscillators (VCXO), temperature-compensated crystal oscillators (TCXO), oven-controlled crystal oscillators (OCXO), temperature-compensated-voltage controlled crystal oscillators (TCVCXO), oven-controlled voltage-controlled crystal oscillators (OCVCXO), microcomputer-compensated crystal oscillators (MCXO), and rubidium crystal oscillators (RbXO).

Crystal Parameter Equations

Equation 1. Series Frequency (Fs)

Equation 2. Load Frequency (FL)

Equation 3. R1 Ohms (@Series Resonance)

Equation 4. Pullability Crystal Unit Equivalent Circuit
The electrical circuit which has the same impedance as the unit in the immediate neighborhood of resonance.



Current
The net transfer of electric charge per unit of time.

CW
Abbreviation for continuous wave.

Cycle
One complete repetition of an event.

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dB Bandwidth
The specified reference level for the difference between the frequency limits of a band containing the useful frequency components of a signal.

dB
Abbreviation for decibel. See decibel.

dBc
Decibels with respect to or relative to the carrier power.

dBm
Decibels with respect to 1 mW. dBm is used in communication work as a measure of absolute power values. Zero dBm equals one milliwatt.

dBW
Decibels with respect to 1 W. Watts of power expressed in decibels.

DC
Abbreviation for direct current.

DCS
Abbreviation for distributed communications system or digital cellular system.

DDS
Abbreviation for direct digital synthesis.

Decibel
Abbreviation = dB. A unit for describing the ratio of two powers or intensities, or the ratio of a power to a reference power.

DECT
Abbreviation for Digital European cordless telephone.

Desired frequency
See nominal frequency.

Deviation
The amount by which a quantity differs from its nominal value. The amount by which a frequency differs from the nominal or specified frequency.

Dew Point
The temperature at which a condensable component of a gas starts to condense into a liquid.

Dice (Quartz)
Pieces of quartz produced by sectioning quartz wafers into rectangular shapes. Dice are then further machined to produce crystal blanks.

Dielectric
Material that does not conduct electricity readily, i.e., an insulator. A good dielectric should also have other properties: It must resist breakdown under high voltages; it should not itself draw appreciable power from the circuit; it must have reasonable physical stability; and none of its characteristics should vary much over a fairly wide temperature range. One important application of dielectrics is as the material separating the plates of a capacitor.

Digital signal processor (DSP)
A specialized, programmable computer processing unit that is able to perform high-speed mathematical processing.

DIL
Abbreviation for dual in-line.

DIP
Abbreviation for dual in-line package.

Direct broadcast satellite (DBS)
A high-powered satellite that transmits or retransmits signals which are intended for direct reception by the public. The signal is transmitted to a small earth station or dish (usually 18-inches) mounted on homes or other buildings.

Direct piezoelectric effect
The generation of electricity (or electric polarity) in crystals subjected to mechanical stress.

Directional antenna
An antenna in which the radiation pattern is not omnidirectional, i.e., a nonisotropic antenna.

Disciplined oscillator (DO)
An oscillator whose output frequency is continuously steered (often through the use of a phase locked loop) to agree with an external reference. For example, a GPS disciplined oscillator (GPSDO) usually consists of a quartz or rubidium oscillator whose output frequency is continuously steered to agree with signals broadcast by the GPS satellites.

Dish
A circular antenna used to pick up transmissions broadcast from a satellite. See satellite dish.

DOD master clock
The master clock to which time and frequency measurements for the U.S. Department of Defense are referenced, i.e., are traceable. The U.S. Naval Observatory master clock is designated as the DOD Master Clock.

Double rotated quartz cut
SC cut, IT cut, and FC cuts are examples of double rotated quartz cuts. Double rotated quartz cut refers to the two rotations from two reference planes needed for these cuts.

Downlink
A link from a satellite to an earth station.

Drive level
The amount of power dissipation in the crystal, expressed in microwatts or milliwatts. Maximum power is the most power the device can dissipate while still maintaining operation with all electrical parameters guaranteed. Drive level should be maintained at the minimum levels necessary to initiate proper start-up and assure steady state oscillation. Excessive drive level can cause poor aging characteristics and crystal damage.

Dry Nitrogen
Moisture free nitrogen.

DTCXO
Abbreviation for Digitally Temperature Compensated Crystal Oscillator.

DUT
Abbreviation for device under test.

Duty cycle
The measure of output waveform uniformity. This term, also referred to as symmetry, is a measurement of the time that the output waveform is in a logic high state, expressed as a percentage (%). This parameter is measured at a specified voltage threshold or at a percentage of the output waveform amplitude.

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Earth station
A station located either on the Earth's surface or within the major portion of the Earth's atmosphere and intended for communication:
* with one or more space stations; or
* with one or more stations of the same kind by means of one or more reflecting satellites or other objects in space.

ECL
Abbreviation for emitter-coupled logic.

EEPROM
Abbreviation for electrically erasable programmable read-only memory.

EIA
Abbreviation for Electronic Industries Association.

Electrode capacitance
This capacitor is not a result of the acoustic vibration of the crystal blank but rather a simple capacitor formed by a dielectric with electrodes on either side.

Electrodes
Terminal through which electric current passes between metallic and nonmetallic parts of an electric circuit. In most familiar circuits current is carried by metallic conductors, but in some circuits the current passes for some distance through a nonmetallic conductor.

Electromagnetic compatibility (EMC)
The condition which prevails when telecommunications equipment is performing its individually designed function in a common electromagnetic environment without causing or suffering unacceptable degradation due to unintentional electromagnetic interference to or from other equipment in the same environment.

Electromagnetic interference (EMI)
An engineering term used to designate interference in a piece of electronic equipment caused by another piece of electronic or other equipment. EMI sometimes refers to interference caused by nuclear explosion.

Electromagnetic spectrum
The range of frequencies of electromagnetic radiation from zero to infinity. Note: The electromagnetic spectrum was, by custom and practice, formerly divided into 26 alphabetically designated bands. This usage still prevails to some degree. However, the ITU formally recognizes 12 bands, from 30 Hz to 3000 GHz. New bands, from 3 THz to 3000 THz, are under active consideration for recognition.

Emission
In this context, radiation produced by a radio transmitting station.

Emitter
A transistor region from which charge carriers that are minority carriers in the base are injected into the base, thus controlling the current flowing through the collector; corresponds to the cathode of an electron tube.

Enable/Disable
The enable/disable pin is similar to an on/off switch. A low or logic 0 on the enable/disable causes the unit not to oscillate. A
"high" or logic 1 on the enable/disable pin allows the unit to work as normal (enabled) producing the specified output.

Energy trapping
A term applied to the application of the cutoff phenomenon in wave guides to suppress undesired modes of vibration in a quartz crystal unit.

Equivalent circuit
The equivalent circuit shown below depicts electrical activity of a quartz crystal unit operating at its natural resonant frequency. The CO, or shunt capacitance, represents the capacitance of the crystal electrodes plus the capacitance of the holder and leads. R1, C1, and L1 compose the "motional arm" of the crystal, and are referred to as the motional parameters. The motional inductance (L1) represents the vibrating mass of the crystal unit. The motional capacitance (C1) represents the elasticity of the quartz, and the resistance (R1), represents bulk losses occurring within the quartz.

Equivalent series resistance (ESR)
The resistive element, measured in ohms, of a crystal device. The ESR measurement is made only at the series resonant frequency (FS), not at some predetermined parallel resonant frequency (FL). The motional inductance (L1) and motional capacitance (C1) are of equal ohmic value but are exactly opposite in phase. The net result is that they cancel one another and only a resistance remains in the series leg of the above equivalent circuit. Crystal resistance measured at some parallel load resonant frequency is often called the "effective" resistance. (2) A term used to define and quantify the resistive element of a crystal.

ESD
Abbreviation for electrostatic discharge.

Etch
A process used in the manufacture of some types of crystal units. The etch process results in an improved surface condition and an increase in the frequency of a blank. The word "etch" is also used to describe the material used in the etch process, as well as the process itself.

ETSI
Abbreviation for European Telecommunications Standards Institute. A European counterpart to ANSI. It facilitates integration of telecommunications standards into all of Europe.

Extremely high frequency (EHF)
Frequencies from 30 GHz to 300 GHz.

Extremely low frequency (ELF)
Frequencies from 30 Hz to 300 Hz.

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Face
One of the natural surfaces that develop on a crystal during the growth process. Often called a "natural face".

Fall time
Fall time is defined as the transition time from an output logic high to an output logic low and is measured in nanoseconds (nSec). This transition time is measured at specified voltage thresholds or at specified percentages of the output waveform amplitude. See rise time.

Family radio service (FRS)
A very low power, short range two-way radio service in the 460 MHz band.

Fanout
Number of IC gates which can be connected to the output of a crystal oscillator.

Farad
Unit of electrical capacitance, equivalent to 1 coulomb of stored charge per volt of applied potential difference. Named for Michael
Faraday.

FC cut
This cut has an improved temperature and frequency characteristic for ovenized applications (OCXO). The frequency vs. temperature curve is a sine with the inflection temperature at ~ +52"C. This crystal operates in the thickness shear mode. Preferred for ovenized oscillators (OCXO) such as space systems, and Global Positioning Satellite Systems. See AT cut, BT cut, IT cut and SC cut.

FCXO
An abbreviation for a Frequency Converting Crystal Oscillator. An FCXO consists of a low phase noise VCXO combined with a complete PLL, which simplifies the synchronization of an output frequency to a stable reference frequency. With its low phase noise, this compact surface mount device is applicable to a wide variety of synchronization schemes. An FCXO also offers a higher degree of component integration than older technologies.

FDD
Abbreviation for frequency division duplex.

Federal Communications Commission (FCC)
An independent federal governmental agency, authorized by the Communications Act of 1934, with authority delegated by Congress to manage commercial and private spectrum.

FER
Abbreviation for frame error rate.

Field-effect transistor (FET)
A field-effect transistor (FET) is a type of transistor commonly used for weak-signal amplification (for example, for amplifying wireless signals). The device can amplify analog or digital signals. It can also switch DC or function as an oscillator.

Filter
Any transmission network used in electrical systems for the selective enhancement of a given class of input signals.

FIR
Abbreviation for finite impulse response.

First in, first out (FIFO)
A queuing discipline in which entities in a queue leave the queue in the same order in which they arrive.

Footprint
In satellite communications, that portion of the Earth's surface over which a satellite antenna delivers a specified amount of signal power under specified conditions.

Forward Error Corrections (FEC)
A system of error control for data transmission wherein the receiving device has the capability to detect and correct any character or code block that contains fewer than a predetermined number of symbols in error.

Frequency
The range of electromagnetic waves with a frequency or wavelength suitable for utilization in radio communication. The periodic repetition of an event within a unit of time. In an electrical circuit, the number of waves that pass a given point in one second. The number of times a resonator plate oscillates or vibrates in one second. The nominal or desired frequency specified by a customer.

Frequency accuracy
The degree of conformity of a measured or calculated frequency to its definition. Since accuracy is related to the offset from an ideal value, frequency accuracy is usually stated in terms of the frequency offset. Frequency Calibration Tolerance @ 25°C
Frequency Calibration Tolerance is the minimum and the maximum frequency deviation allowed from the Target Frequency @25°C. This deviation is usually specified in ±ppm (parts per million).

Frequency deviation
The amount by which a frequency differs from a prescribed value, such as the amount an oscillator frequency drifts from its nominal frequency. In frequency modulation, the absolute difference between (a) the maximum permissible instantaneous frequency of the modulated wave or the minimum permissible instantaneous frequency of the modulated wave and (b) the carrier frequency.

Frequency drifting
An undesired progressive change in frequency with time. Causes of frequency drift include component aging and environmental changes.

Frequency fluctuation
A short-term variation, with respect to time, of the frequency of an oscillator.

Frequency hopping, spread spectrum (FHSS)
Frequency hopping is one of two basic modulation techniques used in spread spectrum signal transmission. It is the repeated switching of frequencies during radio transmission, often to minimize the effectiveness of "electronic warfare" - that is, the unauthorized interception or jamming of telecommunications. It also is known as frequency- hopping code division multiple access.

Frequency instability
See frequency stability.

Frequency modulation or frequency modulated (FM)
In frequency modulation, the frequency of the carrier wave is varied in such a way that the change in frequency at any instant is proportional to another signal that varies with time. See phase modulation.

Frequency offset
The difference between a measured frequency and an ideal frequency with zero uncertainty. This ideal frequency is called the nominal frequency.

Frequency range
A continuous range or spectrum of frequencies that extends from one limiting frequency to another. The frequency range for given equipment specifies the frequencies at which the equipment is operable. For example, filters pass or stop certain bands of frequencies. The frequency range for propagation indicates the frequencies at which electromagnetic wave propagation in certain modes or paths is possible over given distances.

Frequency shift
A change in the frequency of a radio transmitter or oscillator.

Frequency-shift keying (FSK)
Frequency modulation in which the modulating signal shifts the output frequency between predetermined values.

Frequency stability
The amount of frequency deviation from the ambient temperature frequency over the operating temperature range. This deviation is associated with a set of operating conditions including operating temperature range, load capacitance, and drive level. This parameter is specified with a maximum and minimum frequency deviation, expressed in percent (%) or parts per million (ppm). The frequency stability is primarily determined by the type of quartz cut and angle of the quartz cut. Some of the secondary factors influencing frequency stability include mode of operation, drive level, load capacitance, and mechanical design. The frequency stability is the allowable deviation, in parts per million (ppm), over a specified temperature range. The deviation is referenced to the measured frequency at +25°C.

Frequency standard
A stable oscillator used for frequency calibration or reference.

Frequency tolerance
The amount of frequency deviation from a specified center frequency at ambient temperature (referenced at 25°C). This parameter is specified with a maximum and minimum frequency deviation, expressed in percent (%) or parts per million (ppm). This deviation is associated with a set of operating conditions including load capacitance and drive level.

Frequency tolerance/stability
An "inclusive" specification is defined as the amount of frequency deviation from the center frequency associated with a set of operating conditions including operating temperature range, supply voltage, and output load. This parameter is specified with a maximum and minimum frequency deviation, expressed in percent (%) or parts per million (ppm).

Frequency translation
The transfer of signals occupying a specified frequency band, such as a channel or group of channels, from one portion of the frequency spectrum to another, in such a way that the arithmetic frequency difference of signals within the band is unaltered.

Fundamental frequency
The lowest frequency at which a resonator plate will oscillate. This frequency is determined by the physical dimensions of the plate. Also known as the first harmonic. See overtones.

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GaAs
Abbreviation for gallium arsenide.

Gain
A measure of the ability of an antenna to receive radio frequency signals, which is related to physical size. The larger the antenna, the higher the gain and the higher the received signal level, in general. An increase in signal power denoted in dbs.

GaN
Abbreviation for gallium nitride.

Gaussian function
A mathematical function used to design a filter which passes a step function with zero overshoot with maximum rise time.

Geometry
The shape of the resonator plate used in a crystal unit. There are three (3) geometrical forms available: flat, contoured, and beveled.

Geosynchronous satellite
A satellite that orbits the Earth during the same period of time in which the Earth rotates, maintaining a fixed orbit, about 24,000 miles above the Earth.

GFSK
Abbreviation for Gaussian filtered frequency shift keying.

Gigahertz (GHz)
A unit of frequency equal to one billion cycles (or Hertz) per second.

Global Navigation System (GLONASS)
A Russian satellite location technology similar to GPS, global positioning system.

Global positioning system (GPS)
A series of 24 geosynchronous satellites that continuously transmit their position. Used in personal tracking, navigation and automatic vehicle location technologies. See GLONASS.

Global system for mobile communication (GSM)
A public, all-digital cellular network that is standardized worldwide and that uses TDMA techniques for multiplexing at approximately 900 MHz, compressed voice at about 13 kb/s, 16 kb/s circuit-switching technology, and error-correcting algorithms.

GMSK
Abbreviation for Gaussian minimum shift keying.

GPIB
Abbreviation for general-purpose interface bus.

GPRS
Abbreviation for general packet radio service.

Grounded base butler
Oscillator commonly used in the range from 20 to 100 MHz. The circuit is capable of delivering high output power, has medium frequency stability. These are basically amplifiers with a tapped capacitor resonant circuit in the collector.

Group delay distortion
The difference between maximum and minimum group delay in the passband.

Group delay
The time taken for a narrow band signal to pass from the input to the output of a device.

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Harmonic level
Signal strength of the multiples of a fundamental frequency.

HBT
Abbreviation for heterojunction bipolar transistor.

Height Above Average Terrain (HAAT)
Measurement of tower height above surrounding average terrain.

HEMT
Abbreviation for high electron mobility transistor.

Henry
The basic unit of inductance, identified by the letter H. One henry of inductance is produced in a closed circuit by a current changing uniformly at the rate of one Ampere per second.

Hermetic seal
An airtight seal.

Hertz
The basic unit of measurement of frequency, "Hertz" replaces the term "cycle per second". Used to denote one complete occurrence of an event in one second. Hertz is commonly abbreviated as Hz.

High frequency (HF)
Frequencies from 3 MHz to 30 MHz commonly known as shortwave. The carrier frequencies of 5, 10, and 15 MHz within this spectrum are internationally allocated for time and frequency broadcasts, and are used by a number of stations, including NIST radio stations WWV and WWVH.

High-pass filter
A filter that passes frequencies above a given frequency and attenuates all others.

Holder
The complete housing for a quartz resonator plate. The holder includes the base and cover. See can and cover.

Holder capacitance
The sum of the stray capacity contributed by the crystal connected between the two leads of the resonator.

Holder size
The measurement of the base and cover combined.

Home satellite dish (HSD)
A home receiver that permits the consumer to receive existing satellite transmissions.

High-speed circuit-switched data (HSCSD)
High-Speed Circuit-Switched Data is circuit-switched wireless data transmission for mobile users at data rates up to 38.4 Kbps, four times faster than the standard data rates of the Global System for Mobile (GSM) communication standard in 1999. HSCSD is comparable to the speed of many computer modems that communicate with today's fixed telephone networks.

Hydrothermal
A method of growing synthetic quartz using a pressure vessel, calcium chloride or sodium chloride, and a quantity of natural quartz material.

Hypertext transfer protocol (HTTP)
In the World Wide Web, a protocol that facilitates the transfer of hypertext-based files between local and remote systems.

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I and Q
Abbreviation for in-phase and quadrature.

Impedance
The total opposition presented by a circuit or device to the flow of alternating current. Impedance is measured in ohms and is represented by the letter Z.

Inductance
In a device, conductor, or circuit, the inertial property that opposes the flow of current when a voltage is applied. Inductance is identified by the letter "L" and is measured in henries.

Inductor
An electronic component used to introduce inductance into a circuit.

Industrial Telecommunications Association ( ITA)
A Washington, DC trade group serving private wireless licensees such as airlines and oil companies.

Industrial, scientific, and medical (ISM) applications (of radio frequency energy)
Operation of equipment or appliances designed to generate and use locally radio-frequency energy for industrial, scientific, medical, domestic or similar purposes, excluding applications in the field of telecommunications.

Inflection point
An AT-cut crystal has a temperature vs. frequency characteristic that can be represented by a third order polynomial. This curve has a point where the slope is zero and the slope is positive on one side and negative on the other side. This point is defined as the inflection point.

Infrared (IR)
Infrared radiation (IR) or the term infrared alone refers to energy in the region of the electromagnetic radiation spectrum at wavelengths longer than those of visible light, but shorter than those of radio waves.The region of the electromagnetic spectrum bounded by the long-wavelength extreme of the visible spectrum (approximately 0.7 µm) and the shortest microwaves (approximately 0.1 mm).

InGaP
Abbreviation for indium gallium phosphide.

InP
Abbreviation for indium phosphide.

Input current
The amount of current consumption by an oscillator from the power supply, typically specified in milliamps (mA).

Input/output (I/O) device
A device that introduces data into or extracts data from a system.

Insertion loss
The loss in load power due to the insertion of a component or device at some point in a transmission system. (Generally expressed as the ratio in decibels of power received at the load before insertion of the apparatus, to the power received at the load after insertion.)

Insulator
Any of several materials that do not easily permit the passage of electricity.

Integrated circuit (IC)
An electronic circuit that consists of many individual circuit elements, such as transistors, diodes, resistors, capacitors, inductors, and other active and passive semiconductor devices, formed on a single chip of semiconducting material and mounted on a single piece of substrate material. An IC is also referred to as a chip and a microcircuit.

Intermodulation (IM)
The production, in a nonlinear element of a system, of frequencies corresponding to the sum and difference frequencies of the fundamentals and harmonics that are transmitted through the element.

Intermodulation distortion (IMD)
Nonlinear distortion characterized by the appearance, in the output of a device, of frequencies that are linear combinations of the fundamental frequencies and all harmonics present in the input signals.

International Telecommunications Satellite Consortium or International Telecommunications Satellite Organization (INTELSAT)
Organization formed in 1964 with the goal of creating a worldwide satellite system. See COMSAT.

Intermediate frequency (IF)
A frequency to which a carrier frequency is shifted as an intermediate step in transmission or reception.

International shortwave broadcast station
A station that sends programs overseas either for direct reception by listeners abroad or for intermediate reception by overseas relay stations that rebroadcast the programs on shortwave or medium wave stations to nearby audiences.

International Mobile Station Equipment Identity (IMEI)
An equipment identification number, similar to a serial number, used to identify a mobile station.

International Organization for Standardization (ISO)
An international organization devoted to determining standards for international and national data communications and other technical fields.

International Telecommunication Union (ITU)
The international organization that coordinates and publishes telecommunications standards and regulatory and standards information.

International Telecommunication Union-Telecommunication Standardization Sector
The Telecommunication Standardization Sector of the International Telecommunication Union (ITU).

Internet protocol (IP)
A DOD standard protocol designed for use in interconnected systems of packet-switched computer communication networks.

ISM
Abbreviation for industrial, scientific, and medical applications of radio frequency energy. Operation of equipment or appliances designed to generate and use locally radio-frequency energy for industrial, scientific, medical, domestic or similar purposes, excluding applications in the field of telecommunications.

IT cut
This crystal cut has an improved temperature and frequency characteristic for ovenized applications (OCXO). The frequency vs. temperature curve is a sine with the inflection temperature at ~ +78°C. This crystal operates in the thickness shear mode. It is preferred for ovenized oscillators (OCXO) such as space systems, and Global Positioning Satellite Systems. See AT cut, BT cut, FC cut and SC cut.

Itty bitty package (IBP)
Refers to the round compression weld package used to enclose early strip resonators.

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Jitter
The modulation in phase with the frequency of the clock oscillator output

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k
See kilo.

Ka-band
Radio spectrum in the 18 GHz to 31 GHz range used by satellite communications systems.

Kilo
A prefix, abbreviated "k," used to denote units of thousands. One "Kilo" is one thousand. A frequency of one kilohertz is a frequency of one thousand hertz (cycles per second). A unit of frequency denoting one thousand (103) Hz.

Kilobyte (kB)
As a measure of computer memory or storage, a kilobyte (KB or Kbyte) is approximately a thousand bytes (actually, 2 to the 10th power, or decimal 1,024 bytes).

KiloHertz (kHz)
Used to describe the frequency of a crystal or oscillator in terms of thousands of Hertz (cycles per second). A frequency specified as "10.0 kHz" would be understood as being a frequency of 10,000 Hertz (cycles per second). A frequency specified as "10,000 kHz" would be understood as being a frequency of 10,000,000 Hertz (cycles per second).

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L1
Abbreviation for motional inductance.

Land Mobile Communications Council (LMCC)
A trade group of frequency coordinators and associations serving private users and commercial operators.

Land mobile radio
Land mobile radio refers to two-way communication between base stations and mobile, terrestrial based mobile radios.

Land mobile service
A mobile service between base stations and land mobile stations, or between land mobile stations.

Land mobile station
A mobile station in the land mobile service capable of surface movement within the geographical limits of a country or continent.

Lapping
Moving a quartz crystal slab over a flat plate on which a liquid abrasive has been poured, to obtain a flat polished surface or to reduce the thickness a carefully controlled amount.

L-band
A range of frequencies covering approximately 1-1.7 GHz.

LDMOS
Abbreviation for laterally diffused metal oxide silicon.

Leads
See pins.

Line of sight (LOS)
Of an electromagnetic wave, propagation in which the direct ray from the transmitter to the receiver is unobstructed, i.e., the transmission path is not established by or dependent upon reflection or diffraction.

Linearity
The relationship that exits between two quantities when a change in one of them produces a directly proportional change in the other. A trade group of frequency coordinators and associations serving private users and commercial operators.

LNA
Abbreviation for low-noise amplifier.

LO
Abbreviation for local oscillator.

Load
The reactance value presented to the crystal by the external oscillator circuit. The power consumed by a device or circuit in performing its function. A power-consuming device connected to a circuit.

Load capacitance
The value of capacitance used in conjunction with the crystal unit. Load capacitance is a parameter specified by the customer, typically expressed in pF (picoFarads).

Load drive capability
The maximum load the oscillator can drive specified in terms of the number of gates or the type of load circuit.

Load resonance
The condition existing when a crystal unit is operated in conjunction with load capacitance. See series resonance.

Load resonance resistance (RL)
The resistance of the crystal unit in series with a stated external capacitance at the load resonance frequency.

Local multipoint distribution service (LMDS)
A system for broadband microwave wireless transmission direct from a local antenna to homes and businesses within a line-of-sight radius, a solution to the so-called last-mile technology problem of economically bringing high-bandwidth services to users. LMDS is an alternative to installing optical fiber all the way to the user or to adapting cable TV for broadband Internet service.

Logic compatibility
In the past, CMOS, TTL, and ECL oscillators were only capable of driving output loads of the same logic family. With the introduction of HCMOS logic, dual compatible oscillators are manufactured that can drive two logic families. The dual compatible oscillator's output waveform voltages are derived from HCMOS logic. The logic output exceeds the minimum voltage level requirements of TTL, and with the higher output current capability of HCMOS, these dual compatible oscillators can drive both logic families.

Logic Levels
Defined as the Output Voltage Logic High or "Logic 1" and the Output Voltage Logic Low or "Logic 0" (See Image below).





Loop
A communications channel from a switching center or an individual message distribution point to the user terminal. Go-and-return conductors of an electric circuit; a closed circuit. A closed path under measurement in a resistance test. A type of antenna, in the form of a circle or rectangle, usually used in direction-finding equipment and in UHF reception.

Low frequency
The part of the radio spectrum ranging from 30 to 300 kHz. A number of standard time and frequency signals are broadcast in this region, including the 60 kHz signal from NIST Radio Station WWVB, and the 100 kHz LORAN-C signals.

Low phase noise crystals
Crystals designed to have a pure spectral signal for such critical applications as communications and radar. See precision crystals.

LPF
Abbreviation for low-pass filter.

Large scale integration(LSI)
LSI (large-scale integration) meaning microchips containing thousands of transistors.

LTCC
Abbreviation for low-temperature co-fired ceramic.

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Mask
In communications systems, to obscure, hide, or otherwise prevent information from being derived from a signal. Masking is usually the result of interaction with another signal, such as noise, static, jamming, or other forms of interference.

Master frequency generator
In frequency-division multiplexing (FDM), equipment used to provide system end-to-end carrier frequency synchronization and frequency accuracy of tones.

Maximum usable frequency (MUF)
In radio transmission using reflection from the regular ionized layers of the ionosphere, the upper frequency limit that can be used for transmission between two points at a specified time.

MCXO
Microcomputer compensated crystal oscillator often used in spread spectrum system clocks, MTI radars, wireless base stations, telecom timing modules, and precision test equipment.

MDS
Abbreviation for multipoint distribution systems.

Mechanical strip
See AT strip.

Medium frequency (MF)
Frequencies from 300 kHz to 3000 kHz.

Mega
A prefix, abbreviated "M", used to denote units of millions. One "Mega" is equal to one million. In our industry, one MegaHertz is a frequency of one million Hertz (cycles per second).

MegaHertz (MHz)
Used to describe the frequency of a crystal or oscillator in terms of millions of Hertz (cycles per second). A frequency specified as "10.0 MHz" would be understood as being a frequency of 10,000,000 Hertz (cycles per second).

Metal-oxide semiconductor field-effect transistor (MOSFET)
A special type of field-effect transistor (FET) that works by electronically varying the width of a channel along which charge carriers (electrons or holes) flow. The wider the channel, the better the device conducts.

Microbalance
An unsealed plated quartz crystal wafer used to measure very minute changes in its mass by monitoring its frequency.

Microprocessor crystal
Standard crystals for use in clock circuits of microprocessors.

Microwave
RF signals between 890 MHz and 20 GHz. Point-to-point microwave transmission is commonly used as a substitute for copper or fiber cable.

Microwave band
Those frequencies from about 1 GHz upward that use microwave frequencies for point-to-point and point-to-multipoint communications, including common carriers, cable TV operators, broadcasters and private operational fixed users.

Microwave radio
A radio frequency used extensively for long-distance telephone transmission. Digitally encoded messages are sent through microwave channels either between terrestrial antennae, via satellite, or through waveguides.

Military crystals
Quartz crystals that are designed to meet military specifications (Mil-Spec) and produced to Mil-Spec requirements (QPL).

Milli
A prefix, abbreviated "m", used to denote units of thousandths. One "milli" is equal to 1/1000th of a unit.

MMIC
Abbreviation for monolithic microwave integrated circuit.

Mobile earth station
An Earth station in the mobile-satellite service intended to be used while in motion or during halts at unspecified points.

Mobile service
A radiocommunication service between mobile and land stations, or between mobile stations.

Mobile station
A station in the mobile service intended to be used while in motion or during halts at unspecified points.

Mode of operation
The mode of operation of a quartz device is one of the factors that will determine the frequency of oscillation. For AT-cut quartz crystals, overtone modes are at odd frequency harmonics. A crystal may operate at its fundamental frequency of 10 MHz, or at odd harmonics of approximately 30MHz (Third Overtone), 50MHz (Fifth Overtone), and 70 MHz (Seventh Overtone).

Modulation
Impressment of information on a carrier signal by varying one or more of the signal's basic characteristics: frequency, amplitude and phase.

Monolithic crystal
A crystal with two or more electrodes where energy is coupled between the electrodes by way of the vibrating quartz structure.

Monolithic crystal filter (MCF)
Filter which is a crystal with two or more electrodes where energy is coupled between the electrodes by way of the vibrating quartz structure.

Motional capacitance
A parameter associated with a quartz crystal unit, used to illustrate the electronic equivalence of the mechanical elasticity of the unit. Motional capacitance may be abbreviated as "Cm" or "C1." The actual value of C1 has physical limitations when it is realized in a quartz crystal design. These constraints include the mode of operation, the quartz cut, the mechanical design, and the nominal frequency of the crystal.

Motional inductance
A parameter associated with a quartz crystal unit, used to illustrate the electronic equivalence of the mechanical mass of the unit. Motional inductance may be abbreviated as "Lm" or "L1."

Motional resistance
The energy lost within the vibrating area of the crystal resonator. Does not include any loss external to the vibrating crystal. It is represented in the electrical circuit as a resistor. See resistance.

MS/s
Abbreviation for million of samples per second.

Multichannel multipoint distribution service (MMDS)
A broadcasting and communications service that operates in the ultra-high-frequency (UHF) portion of the radio spectrum between 2.1 and 2.7 GHz. MMDS is also known as wireless cable.

Multi-element dipole antenna
An antenna consisting of an arrangement of multiple dipole antennas.

Multipoint distribution service (MDS)
Also known as "wireless" cable. This is a one-way, domestic public radio service broadcast on microwave frequencies from a fixed station that transmits (usually in an onmidirectional pattern) to multiple receiving facilities located at fixed points.

Multi-satellite link
A radio link between a transmitting Earth station and a receiving Earth station through two or more satellites, without any intermediate Earth station.

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n
The small letter "n" is used to designate the overtone number of a crystal unit.

Narrowband AMPS
Cellular standard that expands the network capacity by up to three times by decreasing the duplex RF channel size to 20 kHz (from 60 kHz).

Narrowband radio
Uses a voice channel with a nominal 3-kHz bandwidth.

Narrowband radio voice frequency (NBRVF)
In narrowband radio, the nominal 3-kHz bandwidth allocated for single channel radio that provides a transmission path for analog and quasi-analog signals.

National Telecommunications and Information Administration (NTIA)
The federal government's spectrum management.

Natural frequency
Of an antenna, the lowest frequency at which the antenna resonates without the addition of any inductance or capacitance.

Necessary bandwidth
For a given class of emission, the width of the frequency band which is just sufficient to ensure the transmission of information at the rate and with the quality required under specified conditions.

Nominal frequency
The specified "name plate frequency" of a crystal or oscillator.

NTC
Abbreviation for negative temperature coefficient.

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OCVCXO
Oven controlled/voltage controlled crystal oscillator often used in often used in navigation system clocks, frequency standards, MTI radars, wireless base stations, telecom timing modules, precision test equipment, phase lock loop (PLL) circuits in telecom timing recovery, wireless base station channel or timing reference and fiber optic timing reference.

OCXO
Oven-controlled crystal oscillator often used in navigation system clocks, frequency standards, MTI radars, wireless base stations, telecom timing modules and precision test equipment.

Ohms
A unit of electrical resistance, defined as the resistance in a circuit in which a potential difference of one volt creates a current of one ampere; hence, 1 ohm equals 1 volt/ampere.

Omni-directional antenna
Antenna that radiates equal power in all directions in a horizontal plane.

Operating temperature range
The maximum and minimum temperatures that the crystal device can be exposed to during oscillation. Temperature range over which the crystal's characteristics are guaranteed. See storage temperature range.

Operation Mode
The Operation Mode for AT cut quartz crystals is at the fundamental mode or an odd frequency harmonic of the fun damental frequency. For example, a crystal may operate at its fundamental frequency of 10 Mhz, or at odd harmonics: 30 Mhz (3rd overtone), 50 Mhz (5th overtone), and 70 Mhz (7th overtone). Original Equipment Manufacturer (OEM)
Maker of equipment that is marketed by another vendor, usually under the name of the reseller. The OEM may only manufacture certain components, or complete computers, which are then often configured with software, and/or other hardware by the reseller.

Oscillation mode
A quartz crystal is designed to vibrate on its fundamental frequency or one of its overtones. This becomes important between the 24 MHz to 40 MHz range. Crystals in that frequency range may be made as either a high fundamental or a low 3rd overtone. Fundamental mode crystals at these frequencies become more expensive, because the quartz blank is extremely thin, difficult to handle, and subject to a higher rate of breakage in processing. If you are able to use the 3rd overtone crystal instead of the fundamental, your cost savings may be significant. As the frequency range is extended, the oscillation mode of the crystal changes to other overtones. Crystals in the range of 60-110 MHz are generally 5th overtones, while crystals in the range of 110-175 MHz generally are 7th overtones.

Oscillator
An electronic circuit that produces an output signal of a specific frequency. An oscillator generally consists of an amplifier having part of its output returned to the input by means of a feedback loop; the necessary and sufficient condition for oscillation is that the signal, in passing from input to output and back to input via the feedback loop, arrive at the input with no change in amplitude or phase. If this condition is met for only a single frequency, the output is a pure sine wave; if it is met for more than one frequency, the output is a complex wave. Some oscillators are designed to operate under certain conditions so that the output is a square wave, a triangular wave, or a pulse. In some cases, a very stable mechanical oscillator, such as a specially prepared quartz crystal, may be coupled to an electronic oscillator to enhance its frequency stability.

Output
The output of a hybrid crystal clock oscillator is a highly stable reference signal.

Output enable function
The function to change the output signal.

Output frequency
The frequency signal generated by an oscillator circuit.

Output load
The power-consuming element connected to the output of a circuit.

Output voltage levels
In digital logic, voltage levels are referred to in terms of logic "0" and logic "1". These levels vary depending on the type of output logic required for the application.

Output wave shape
Graph of the output frequency vs. time. This can be a square, sine, or trapezoid.

Ovenized crystals
An ovenized crystal is any crystal made to operate at a temperature above the anticipated ambient temperature (typically +50°C to +110°C) in order to eliminate changes in frequency due to the change in temperature. See precision crystals.

Overshoot/Undershoot
This effect is commonly called ringing. The output voltage can exceed the steady state plateau of either the logic "0" state or the logic "1" state for a period of time. This ringing will decrease in amplitude until the steady state plateau is reached. An unmatched impedance load presented to the oscillator output causes the ringing. It becomes more pronounced as the rise/fall times decrease and the output frequency increases. Proper output loading and good R.F./Microwave transmission line techniques must be used to prevent ringing on the waveform.

Overtone order
The numbers allotted to the successive overtones of a given mode of vibration from the integral numbers commencing with the fundamental