the induction coil is an LC tank of its own. the RLC circuit on the left is a model of a coil with 1k DC resistance, 1H inductance and 100pF capacitance. output frequency is the resonant frequency of the coil.
once the inductance and resonant frequency is known, the capacitance can be found using maths
C=1/((2×pi×f)^2 × L)=100pF
thanks @hurz!
