The 905 and 905R frequency counters are designed for on-site frequency calibration in ATE systems and calibration laboratories. Both models fulfill the requirements for calibrating cell phone base station master clocks with a short warm-up period of less than 10 minutes. They also offer high resolution of 10 digits at 1 second measuring time and dc to 300 MHz standard bandwidth, up to 2.7 GHz optionally. The 905R offers a built-in rubidium frequency reference and maintains a 50 times margin to base station master clock frequency accuracy specification for 10 years without adjustment. The lower cost 905 can be equipped with a highly stable square cut oven oscillator.