Systems with naxiwum pulse flow capacity are discussed. It is shown that the upper limit of the permissible counting rates is set by pile up induced phenomriena, which are analyzed here. The best pulse stretching mode miinimizing pile up is peak value extraction. The basic statistical properties of such a device are investigated. These principles are applied to the design of an electronic system which comprises a fast amplifier, a high speed linear gate and a biased pulse stretcher. The noise properties of the anmplifier were studied using the autocorrelation function mreasured experimrentally. The system allows one to detect a particles with satisfactory pile up performances and negligible spectrum distortion in the presence of back-scattered protons up to 108 counts/sec. Applications to pulsed high energy accelerators are described.