series/parallel combinations of R, L, and C circuits; sinusoidal forcing; complex frequency and Bode plots; mutual inductance and transformers; two port networks.
The post starts with a basic model of a crystal having a series capacitance and inductance along with a resistance. There’s also a shunt or parallel capacitor. When you order a crystal ...
A large-valued parallel resistor models the leakage through the dielectric in series with the ideal capacitance ... for the paralleled capacitance and inductance components.