He stayed up late at night refining his designs, ultimately choosing to manufacture two new products-an attachment plug
and a two-way socket.
The company was founded in 1918, the same year in which it introduced an improved attachment plug
UL's medical equipment standard, UL 60601-1 specifies in section 57.2DV.1 that the mains plug for patient care equipment comply with the requirements for a hospital grade attachment plug (mains plug) per UL's standard for attachment plugs and receptacles, UL 498.
UL 498 is not intended for molded-on attachment plugs (ref.
(4) Inspect attachment plug
for loose, broken, and missing parts.
The forces with which the spring contacts of a receptacle grip the blades of the attachment plug
ensure reliable low-resistance electrical connections.
To insert an attachment plug, its prongs must be placed into the slots of the protective cap, then turned 90[degrees] or until the slots of the outlet are exposed.
* Attachment plugs fit on the ends of cords of portable appliances and permit them to be connected to wall receptacles or extension cords.
Since then, the USITT standard has become the ESTA/ANSI E1.24 standard and has been incorporated in the UL 498 safety standard for attachment plugs
* Heavy-duty attachment plugs for ranges and dryers are much larger than standard attachment plugs.
The different amperage attachment plugs are not interchangeable because of a difference in their configuration.
The back-wiring and side-wiring devices--which include 20-amp/125volt to 30-amp/480-volt devices--are said to comply with NEMA WD6 (Wiring Devices-Dimensional Requirements), UL 498 (Attachment Plugs
and Receptacles), and Federal Specification WC 596 (Electrical Connectors).