I get these all the time, but rarely see them posted here. Please note the exceptions for gliders, and the resulting cautionary statements.
Mike

Your ADS-B Questions Answered: Get the Facts Here
Notice Number: NOTC7911

Question: Last month I read your description of where ADS-B will be required after January 1, 2020. You described ways to identify the rule airspace specified in Title 14 Code of Federal Regulations (14 CFR) section 91.225. Does that mean that every aircraft in “rule airspace” will be equipped with ADS-B Out?

Answer: In general, the answer is yes, however there are exceptions.

Subparagraph (e) of section 91.225 states that “any aircraft that was not originally certificated with an electrical system, or that has not subsequently been certified with such a system installed, including balloons and gliders” does not need to equip with ADS-B Out.

There are a few restrictions as to where these aircraft can fly without ADS-B Out, but you may encounter gliders, balloons, or antique aircraft in rule airspace. A good example is gliders above 10,000 feet mean sea level.

There also could be aircraft with inoperative ADS-B equipment en route to a repair facility that may be authorized by ATC to operate within rule airspace.

The FAA provides an equipage decision tree, Google Earth airspace map, and other online decision tools to help pilots comply with their responsibility to know the equipment and operational requirements of the airspace https://www.faa.gov/nextgen/equipadsb/research.

You can find the actual regulation here (14 CFR 91.225) and you should familiarize yourself with its details. In particular, it is your responsibility to determine whether your aircraft is required to have ADS-B Out.

There is an important safety reason to know that not every aircraft will have ADS-B Out, as well. If you are equipped with ADS-B In, you already know the additional traffic situational awareness value it offers. What may be too easy to forget is that not every aircraft will have or needs to have ADS-B Out.

Avoid complacency. You should always view ADS-B In as an aid to your responsibility to see and avoid; it is not a replacement for it.