The Change-Of-State extension detects whether:

  • A binary object property is equal to a configured alarm value.
  • An enumerated (Unsigned) property is equal to one of a configured set of alarm values.

Supported BACnet object types capable of using Change-Of-State extension:

  • Binary_Input
  • Binary_Output
  • Binary_Value
  • Multistate_Input
  • Multistate_Output
  • Multistate_Value
  • BACnet FLN devices

Property Name



A writable property used to set the size of the Property-State-Values array.


A writable property that holds the alarm value(s) for the extension.


A writable proprietary property that specifies a deadband time, in seconds, that must pass between the time an object first detects an offnormal condition and a to-offnormal event state transition occurs.

Validity Checks

PXC.A will perform validity checks on the Change-Of-State extension properties. These checks are run when the extension is saved in the web UI or when objects are created/edited using BACnet services.


Binary Objects

BACnet service

Property-State-Values-Count can be more than one, but only the first entry in Property-State-Values is used.

  • If the first entry in Property-State-Values is 0, alarm-value will be set to 0 (inactive).
  • If the first entry in Property-State-Values is greater than 0, alarm-value will be set to 1 (active).

Property-State-Values-Count will be set to one, and the first element of Property-State-Values is set to alarm-value.


Multi-state objects

BACnet service

alarm-values = Property-State-Values

Property-State-Values-Count will be set to the number of elements in the alarm-values list, the elements of alarm-values will be copied into Property-State-Values.

If the Object-Name-Reference is not successfully resolved, object-property-reference shall be set to default, reliability shall be set to configuration-error, and the EEO will not detect event states or issue event notifications.