To see one on a chart check out Altus AFB (KLTS). It’s easy to see the chart markings because Altus is located in the middle of nowhere. According to the AIM:
> TRSAs were never controlled airspace from a regulatory standpoint because the establishment of TRSAs was never subject to the rulemaking process; consequently, TRSAs are not contained in 14 CFR Part 71 nor are there any TRSA operating rules in 14 CFR Part 91.
Altus is a good example of why TRSAs still exist. It requires a radar facility only because it has a lot of large aircraft flying around it all the time because it hosts the squadrons conducting initial training for the USAF’s KC-135, C-17, and C-5 aircraft. According to the AIM, TRSAs were originally intended to be converted to ARSAs, but “the ARSA requirements became relatively stringent and it was subsequently decided that TRSAs would have to meet ARSA criteria before they would be converted.” In other words, there’s no need to waste a lot of money converting a perfectly good TRSA to a Class C in a place like Altus.
When I flew out of there it was manned exclusively by military controllers–I don’t know if that’s still the case.