The DSC1123CI2-125.0000T is a 125 MHz LVDS oscillator built on a MEMS resonator, not a quartz crystal — that means it handles the shock and vibration profile of an engine bay or a factory-floor drive cabinet without the frequency drift you'd see from a quartz can. The LVDS output swings 350 mV typical into a 100-Ω differential termination, which is the standard interface for FPGA reference clocks, high-speed ADC/DAC sampling clocks, and SERDES PLL references.
Enable/Disable function and package footprint
The 6-SMD package (3.20 mm x 2.50 mm, 0.88 mm seated height) is a standard 6-pin MEMS oscillator footprint; it is pin-compatible with many SiTime and other MEMS oscillators, so a board designed for a 6-pin 3.2x2.5 mm LVDS oscillator can accept this part without a layout change.
No official second source is listed, but the 6-pin 3.2x2.5 mm LVDS MEMS oscillator footprint is widely used across the industry, so a cross-reference to a SiTime or Epson MEMS part with the same frequency and output type is a practical fallback if supply tightens.