FEI Communications FE-5680A Rubidium Frequency Standard

The FE-5680A is a precision Rubidium Frequency Standard, commonly referred to as a rubidium atomic clock. It is designed and manufactured by FEI Communications, Inc., a subsidiary of Frequency Electronics, Inc. (FEI). These devices are integral to telecommunications, military systems, and scientific research where ultra-stable timing and frequency synchronization are critical.

Originally developed in the United States, these units were primarily manufactured at the company's facilities in Mitchel Field, New York. Frequency Electronics, Inc. remains the ultimate owner, providing high-reliability time and frequency technology for terrestrial and space-based applications. The FE-5680A is well-known in the electronics community for its compact design and its popularity in the secondary market for high-fidelity clock synchronization.