As a young airman back in the 1960s, I was periodically scheduled for CQ (Charge of Quarters). The detail was normally performed in the squadron orderly room, beginning around the time that the commander, first sergeant and orderly room staff left for the day and ending sometime after they returned the next morning. Duties included such things as answering the phones, taking messages, doing security walks around the barracks and generally trying not to make any major screw-ups that might land you in hot water.
The Navy has a similar program which they call The Watch and that's what those of us in pay grades E6 and below pulled at TDC. Think of it as CQ with about 200 years or so of additional naval history and tradition to complicate things.
In the TDC lobby was a glass enclosure, sort of like the ticket window at old movie houses. There was a small room behind it that contained a cot. During the day, the Chief Boatswain's Mate (BMC Gagne when I was there) sat in that enclosure. We came on duty a few minutes before he left and mostly stayed in that enclosure until he returned in the morning.
There was a "squawk box" on the wall that was connected to a similar gadget up in the "Flag Office" where the admiral and general hung out. Whenever the admiral arrived at the main entrance to the building (quarterdeck in NAVSpeak) we'd key the box and announce to whoever was on the other end, "Admiral's aboard!" Same deal for the general. Whenever the admiral walked out the main entrance, we'd similarly announce, "Admiral's ashore!" Again, same deal for the general. Now I was pretty sure that our building wasn't actually a ship so nobody was actually coming aboard, and nobody really had to go ashore because we were already there but I didn't point that out to those in charge. That's just part of the history and tradition stuff I mentioned earlier so I tried not to dwell on it.
Once everyone left for the day, I mostly just sat, read a book, wrote letters, answered the occasional phone call and not much else until about midnight when I locked the place down and tried to sleep on the cot in the back until morning. By the way, I was amazed how many people in the States had no concept of international time zones. It wasn't at all unusual to get a call at O-dark thirty from someplace like Podunk Iowa wanting to speak to someone in the organization.
That was pretty much it, except for raising and lowering the flag in the mornings and evenings, but that deserves its own stroll down memory lane which I'll get to later.