The Brainstorm DXD/OCXO is an optional Oven-Controlled Crystal Oscillator for the DXD series. It achieves a very high frequency stability providing greater long-term time and TOD accuracy (+/-10ppb, equivalent to less than +/-10 frames per year). The DXD/OCXO is particularly recommended when using GPS as the greater stability of the OCXO will minimize drift during long dropouts. After installing the OCXO, no special setting is required. The DXD will automatically use the OCXO as the Internal oscillator and indicate INTERNAL/OCXO on the different displays