Motorola Quantar 5Mhz reference standard UHSO Ultra High Stability Oscillator. These units have 2 part numbers CLN1477 or TLN3459A. Both part numbers are identical, one is the original part number and one is the FRU (Factory Replacement Unit). Units are in great condition and guaranteed fully operational. These units are great for tighter frequency control. Please contact us if you have any questions.