The 501-27583-21 from Quantic Wenzel (Wenzel Associates, Inc.) is a OCXO with Frequency 400 MHz, Supply Voltage 12 V, Phase Noise -107 dBm/Hz@100 Hz to -77 dBm/Hz@10 Hz, Phase Noise 1 kHz -137 dBm/Hz, Phase Noise 10 kHz -152 dBm/Hz. Tags: Module with Connectors. More details for 501-27583-21 can be seen below.