Abstract: A pre-amplifier for photomultiplier tubes includes means to compensate for the combined dark current and noise output of a photomultiplier tube without inducing a noise dependent offset voltage at the pre-amplifier output. A feedback amplifier and a compensating network, including a capacitor, cooperate to monitor the pre-amplifier output and during this time to maintain the feedback amplifier in a linearly responsive state while charging the capacitor to an amount necessary to clamp the average value of the most negative excursion of the pre-amplifier output to ground.

Abstract: An improved electronic integrator enabling compensation or correction for the error in integration due to inherent dielectric absorption in the integrating capacitor. A sampling amplifier samples the error during a sampling interval and develops a correction voltage representative of the error. During the next sequential integration interval the correction voltage is transferred to the integrating capacitor to counteract and thereby compensate for dielectric absorption in the integrating capacitor. Timed control means provide the sequential timing and operation of the apparatus.

Abstract: In a system wherein transitions occur in a data signal encoded with a known format and transition displacements occur as a result of bandwidth limitations, noise, and the like, there is disclosed a method and means for measuring the probability density function associated with such transition displacements. Furthermore, the present system permits the measurement of conditional probability such that the probability density function associated with certain selected transitions can be separately evaluated. The probability density function associated with transition displacements is measured by measuring the average frequency of occurrence of transitions of the data within a narrow, first time interval, varying the first time interval over a larger, second time interval during which transitions of the data are expected to occur, and plotting the average frequency of occurrence of data transitions determined at each first interval.