When checking the matching between the oscillation circuit and the crystal unit, what specific conditions are considered appropriate ? It is mainly evaluated from the following perspectives.

1．Whether the crystal unit oscillates stably
2．Whether the frequency is as targeted
3．Whether abnormal oscillation does not occur
　(e.g., Frequency fluctuates more than expected. Or frequency oscillates at a stable frequency under normal temperature, but the frequency jumps under low or high temperature.)

The following three indicators are used for the above matching evaluation.
1.　Whether the crystal unit oscillates stably→ Negative Resistance
2.　Whether the frequency is as targeted→ Frequency Deviation
3.　Whether abnormal oscillation does not occur→ Level of Drive

Evaluation is performed using these indicators, and if the recommended values and standard values determined by NDK or the characteristic values requested by the customer are not satisfied, the circuit constants including capacitors and resistance values are experimentally examined for optimal oscillation conditions.

＜Glossary＞
* Negative Resistance (-R) : The ability of the circuit to cancel the resistance R of the Crystal unit and oscillate
* Oscillation Frequency (F) : Characteristics depending on Load Capacitance (CL)
* Level of Drive(DL) : Power consumed by the resistance R of the Crystal unit