On November 2, 2017, the United States Federal Communications Commission (FCC) officially announced that in order to simplify the certification process of wireless device equipment and clarify the use of electronic tags, the DoC & VoC plan was officially changed to SDoC.
From November 2, 2017 to November 2, 2018, this year is the transition period. During this transition period, you can continue to use the FCC VoC and DoC certification procedures or use the new FCC SDoC certification procedures. After a one-year transition period, the FCC SDoC certification process will officially replace the original FCC VoC and DoC certification methods.

After the implementation of the new standard, the FCC mode is SDOC mode (for household appliances, consumer electronics, digital electronics and other products), ID mode (for products with wireless transmission function).

https://www.fcc.gov/general/equipment-authorization-procedures#block-menu-block-4