What does the 'CHECK' display on my touchpad mean?

The word CHECK on the touchpad's display, accompanied by beeping, indicates a trouble condition in the system. A CHECK with one or more zone numbers means a problem exists with the displayed zone(s) and requires your attention. If the display persists after correcting the problem and entering the OFF sequence twice, you should call for service. A CHECK 70 indicates a wiring fault with the external sounder, and CHECK 90 indicates RF interference with wireless sensors. (Page 37)