Eaton Bussmann RDF Series Fused Disconnect Switch
How does the test function work?
Example Part Number RDF60J-3-ND
The test function is for testing control circuits using aux contacts (BAC05/BAC06) without energizing the circuit. A little more information can be found here:
UL Branch Circuit Rated Fuses | UL 98/UL 508 Disconnect Switches | Bussmann series | Eaton