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The following technical terms are generally use for crystal units:

Crystal wafer (blank) : A piece of quartz crystal cut as specified in terms of shape, dimensions and orientation.

Electrode : Conductive thin film vacuum-evaporated onto a crystal wafer to allow AC voltage to be applied.

Holder : A case housing a crystal wafer, electrode and support to prevent them mechanically and environmentally from being influenced by outside conditions, and also having terminals permitting the electrical connection of the electrode with an outside circuit.

Crystal unit : Mounted crystal wafer with electrode housed in a holder. Fundmental The lowest frequency at which a specific crystal will vibrate.

Overtone : Odd numbers assigned for frequencies in terms of specified oscillation mode (The first overtone is called fundamental mode, followed by 3rd, 5th and 7th overtones, The frequencies are not exactly three times, five times or seven times the fundamental mode.)

Series resonance frequency : Lower frequency of the two given when the electrical impedance of a crystal unit becomes resistant near resonance point.

Load capacitance : Effective series capacitance measured from the terminals of a crystal unit to oscillation circuit and determined as a condition in the case of using a crystal unit in an oscillation circuit. Operating frequency is determined by the electrical characteristics of a crystal unit and the load capacitance.

Nominal frequency : Nominal value expressed in terms of frequency.

Series resonance : Condition of resonance in the case of limitless load capacitance.

Frequency tolerance : Deviation from the nominal frequency expressed by ratio in reference to nominal frequency.

Equivalent series resistance : Equivalent resistance for series resonance frequency.

Load Resonance Resistance : Resistance for the lower (frequency of the two given when the electrical impedance) becomes resistant near the resonance point of a circuit, with the load capacitance connected with a crystal unit in series.

Operating temperature range : Temperature range within which crystal units operate under specified conditions.

Drive level : Electric-power or current level under the specified conditions of a crystal unit.

Main mode and spurious : Main mode indicates the most prominent resonance frequency and spurious indicate other resonance frequencies when there are some resonance frequencies near the nominal frequency.

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