AECTP 500 is the NATO publication that describes how the electromagnetic environmental effects of a platform are verified, and it is the companion to the publication that defines the environment itself. It addresses a problem that bench testing cannot solve: once equipment is installed, with its cables routed as they are in service and with other systems operating around it, the coupling paths that determine whether the platform is electromagnetically compatible exist only in that installation, so the verification has to be performed on the platform. The document therefore covers the characterisation of the ambient environment in which the measurements are made, the techniques for measuring the emissions of a platform and for subjecting it to fields and injected currents, the transfer function measurements used to relate what can be measured at an accessible point to what is present inside a closed structure, and the criteria by which the platform is judged to be acceptable. It is applied at platform level rather than to individual items.