The new CNT-91R is the first instrument in the Pendulum CNT-90-family that includes a built in ultra-stable atomic clock. The CNT-91R is basically a combination of the ultra-high resolution CNT-91 and a Rubidium Frequency Standard, all in one box. The CNT-91R is an ideal transportable Frequency Calibrator for master clocks and other oscillators, since it combines both an ultra- stable Frequency Reference, and a high-accuracy/high-resolution frequency and phase comparator. The CNT-91R can also be used to analyze/ characterize oscillators, including calculation of Allan Deviation and frequency warm-up performance, thanks to its built-in numerical statistics analysis and the graphic trend plot. The CNT-91R can be used together with the optional Modulation Domain Analysis SW TimeViewTM, for in-depth analysis of jitter, modulation and frequency settling. Customer benefits Transportability: The CNT-91R is an all-inclusive high performance calibrator of frequency sources, including also the highest precision OCXO:s. The compact format, and the short warm-up time, makes the CNT-91R an ideal transportable frequency calibrator Complete frequency calibrator: The following parameters are displayed at a glance on the graphic LCD: - statistical mean value of frequency - Standard and/or Allan Deviation of frequency - Graphic view of initial frequency drift vs time Fast and precise calibration of mean frequency and Allan Deviation (ADEV): The combination of ultra-high stability time-base and resolution enables very fast and accurate frequency calibration. Frequency measurements are made back-to-back with zerodead- time to enable correct calculation of Allan Deviation Oscillator analysis The CNT-91R features true zero-dead-time measurements of frequency and phase (TIE), and can therefore be used for wander and jitter analysis of clocks under test. Zero-dead-time measurements are also a pre-requisite for correct calculation of short term stability expressed as Allan Deviation.