The AR61A – 08 from AccuBeat is a Time and Frequency Standard with Frequency 5 MHz, Frequency Stability ±0.5 ppb, Phase Noise -153 to -70 dBc /Hz, Short Term Stability 0.003 to 0.03 ppb, Long Term Stability 0.04ppb@month, 0.36ppb@year. Tags: Frequency Standard. More details for AR61A – 08 can be seen below.