How does this P-SPXO compare against a fixed frequency SPXO? The SPXO, or Simple Packaged Crystal Oscillator, is also referred to as a fixed-frequency oscillator as it is not field programmable. The frequency of a simple oscillator is fixed and it is dependent on the cut of the crystal. The Silicon IC contains the simple oscillator circuit, followed by an optional divider and an output buffer, typically CMOS levels for single-ended output. For the P-SPXO or Programmable SPXO, output frequency of a blank oscillator has to be programmed either at the factory or out in the field with the SG-Writer II programmer. The circuit is little bit more complicated with the PLL circuit, as mentioned in the previous slide. Epson’s new P-SPXOs, the SG-8018 and SG-8101 Series, contain a 26MHz crystal and a Silicon IC.