First is the load curve, the crystal parallel resonant frequency as a function of external circuit capacity. This is a non-linear curve of the frequency offset of a crystal as a function of load capacity. Second is the tuning curve, which is the inverse of the load curve. The tuning curve gives the load capacity as a function of the crystal frequency and is used to center an oscillator's frequency. refer to application note AN-831 for more details. For other questions not addressed by the Knowledge Base, please submit a techical support request.