In the early days of providing phones in every dorm room, SWBT provided this service at the University of Oklahoma. This was done with Step switches, probably under the centrex tariffs. There were incessant complaints from students of overloads and unending busies.
SWBT did the usual busy studies, ending at 9 or 10 p.m. or whatever the normal time for such studies. Sometoday finally suggested extending the study an hour or two. This showed increasing usage as the hour got later, and the busy study was finally extended long into the wee hours of the night.
The busy hour turned out to be, I forget now whether it was 1 to 2 a.m. or 2 to 3 a.m. Reinforcement of the switches followed in quick time (for a telco).
Wes Leatherock snipped-for-privacy@aol.com snipped-for-privacy@yahoo.com