The 9AC040001820A0D2JB is a DIP Crystal Resonator HC-49S RoHS manufactured by JGHC. It is a small, cylindrical device made of ceramic and metal components. It is a quartz crystal oscillator, which is used in microelectronic circuits to provide a stable and precise timing reference. The device is specifically geared for applications such as Watch, Audio, PC, and Clock Generations. The resonator is RoHS compliant and suitable for lead-free assembly.