  We discuss a signal theorem for charged particle detectors where the finite
propagation time of the electromagnetic waves produced by a moving charge
cannot be neglected. While the original Ramo-Shockley theorem and related
extensions are all based on electrostatic or quasi-electrostatic
approximations, the theorem presented in this report is based on the full
extent of Maxwell's equations and does account for all electrodynamic effects.
It is therefore applicable to all devices that detect fields and radiation from
charged particles.
