The ECLIPSE guided wave radar transmitter is based upon the technology of TDR (time domain reflectometry). TDR utilizes pulses of electromagnetic energy transmitted down a wave guide (probe). When a pulse reaches a liquid surface that has a higher dielectric constant than the air (εr = 1) in which it is traveling, a portion of the pulse is reflected. The transit time of the pulse is then measured via ultra speed timing circuitry that provides an accurate measure of the liquid level.