Nortel MICS 7.1, about 10 7310, 4 7208, 1 7410CT (I know), 5 7406 on 2 base stations, 3 doorphones, 1 ASM. KSU and ASM are on a UPS.
On day last week, one 7310 decided to call another set... would not stop until the called station answered (no camp-on or busy call-back, that set hardly gets...