Time domain coupling from an incident plane wave pulse to a device on a printed circuit board inside of a metallic cavity enclosure is calculated and studied, using an efficient hybrid method. The cavity has an exterior feed wire that penetrates through an aperture and makes direct contact with the printed circuit board trace that leads to the device. The signal level at the input port of the device is calculated and studied. The incident electromagnetic field is assumed to be a time domain plane wave in the form of a pulse, and two pulse shapes (a Gaussian pulse and an exponentially damped sinusoidal pulse) are studied. Results show how different pulse characteristics produce different types of signals at the input to the device. The time domain results are validated by comparing with simple expressions based on the resonant frequencies and the quality factor of the cavity.