What is the purpose of zones 970 and 971 on the VISTA-128FBP?
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Zones 970 and 971 are system trouble zones used to monitor the panel's Notification Appliance Circuits. Specifically, zone 970 represents Bell 1 Output and zone 971 represents Bell 2 Output (Page 60) [1].
A "CHECK" or "TRBL" display accompanied by these numbers indicates that a system trouble exists on the corresponding bell output (Page 60) [1].