The four-page security note, a copy of which was reviewed by Reuters, said that undocumented cellular radios had been discovered “in certain foreign-manufactured power inverters and BMS,” referring to battery management systems.

The note, which has not previously been reported, did not specify where the products containing undocumented equipment had been imported from, but many inverters are made in China.

It’s got to be easier to pick up on them at the cell network level, if they’re connecting to the cell network. You’re not going to inspect every power-connected device for a cell radio.

It’d be harder to deal with non-cell radios, like shortwave receivers or something.