Under NCAA rules, Rule 2; Section 12,(Duties of Timer)Article 9 - states that a warning signal is to occur 15 seconds before the expiration of an intermission. In my own personal experience reffing high school basketball, this practice is not followed. I'm curious if this is adhered to your area??? I believe the purpose of this was to give coaches warning that subs had to be made before the 2nd signal signifying the end of the intermission.
Any comment???

While the NF rule is the same, in my area (CT) we've always buzzed at 1:00 so that everyone is ready at (or before) :00.

When I do not see a team on the floor with 1:00 left in the half-time intermission, I ask the timer (if I can find one) to give me a practice buzzer.
For some reason the teams are not always notified at 3:00.

We generally use the warning buzzer at 0:15.

mick

We buzz at 1:00.