The Clock,master Regulating, cataloged under National Stock Number 6645-01-063-0399, is classified within Federal Supply Class 6645 (Time Measuring Instruments) of the Instruments and Laboratory Equipment group. The manufacturer of record is Frequency Electronics Inc. The record lists 2 manufacturer part numbers for this item, enabling identification through both NSN and commercial part number lookups. 2 additional reference documents (drawings, advisory and superseded references) are recorded in the U.S. Government catalog. Current acquisition status: Active.
| Parameter | Value |
|---|---|
| NSN | 6645-01-063-0399 |
| Primary Part Number | 21750-6200 |
| Item Name | Clock,master Regulating |
| FSC / FSG | 6645 / 66 — Time Measuring Instruments |
| Manufacturer | Frequency Electronics Inc |
| Status | ACTIVE |
| Acquisition Status | ACTIVE |
| DEMIL Code | DEMIL F — Mutilate — Cut |
| Hazard | No hazard code in the DLA record (HMIC N) |
| Criticality Code | X |
| Part Number | Manufacturer |
|---|---|
| 21750-6200 | Frequency Electronics Inc (USA) |
| FE-5440A | Frequency Electronics Inc (USA) |
| Reference | Meaning |
|---|---|
| TD-1251/U | 5/2 Secondary reference U.S. Government activity |
| 583R784H01 | 3/2 Design control — primary reference U.S. Government activity |
NSN 6645-01-063-0399 is a Clock,master Regulating, manufactured by Frequency Electronics Inc, classified under FSC 6645, Time Measuring Instruments. Status: active.
NSN 6645-01-063-0399 has 2 manufacturer part numbers on file: 21750-6200 (Frequency Electronics Inc), FE-5440A (Frequency Electronics Inc).
Key specifications for 21750-6200: Special Features: OUTPUTS:SECOND MARK, REAL TIME DATA (RTD), RTD TRANSFER CLOCK, REAL TIME TRANSFER GATE, 1 MHZ SINUSOIDAL, 1 FRONT, 5 MHZ SINUSOIDAL, 1 FRONT, 3 MHZ SQUARE WAVE; 3.01 0.5 VOLTS, PEAT-TO-PEAK INTO A 75 OHM LOAD, USES CESIUM BEAM FREQUENCY STANDARD AND INTERNAL BATTERY IN PORTABLE CASE MHz. 0 specifications are documented in the U.S. Government catalog.
No hazard code in the DLA record (HMIC N). Hazard information on this page is shown exactly as it appears in the DLA record.
NSN 6645-01-063-0399 has DEMIL Code F. Demilitarization may be required before disposal or transfer to non-military entities.
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-16.
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-18.