Can't really think of any in game signals needed between the table and officials.
If the scorer needs to get my attention, then there's a horn for that. If the timer somehow needs to get my attention, he's going to be using that horn as well. I don't know how the table would try and get an official's attention to alert them of a minute left. When I'm going up and down the court, I'm not going to be looking at the table. The scorer is also going to be alerting officials of penalty situations during dead ball situations where the calling official is most likely near the table, so again, no signals needed.
If for some reason the scoreboard malfunctions and the timer has to alert the officials as to the end of the period, I'd just ask game management to find a whistle/horn and stop watch, and tell the timer to use it when time has expired (I've actually had to go that route. Clock stopped working with two minutes left in the game).