diff --git a/xyz/openbmc_project/Sensor/Threshold/Critical.interface.yaml b/xyz/openbmc_project/Sensor/Threshold/Critical.interface.yaml
index 9dea127..1c8b4bc 100644
--- a/xyz/openbmc_project/Sensor/Threshold/Critical.interface.yaml
+++ b/xyz/openbmc_project/Sensor/Threshold/Critical.interface.yaml
@@ -42,3 +42,36 @@
 
           CriticalAlarmLow may be set to False to clear an alarm condition.
           The behavior of setting CriticalAlarmLow to True is undefined.
+signals:
+    - name: CriticalHighAlarmAsserted
+      description: >
+          The high threshold alarm asserted.
+      properties:
+         - name: SensorValue
+           type: double
+           description: >
+               The sensor value that triggered the alarm change.
+    - name: CriticalHighAlarmDeasserted
+      description: >
+          The high threshold alarm deasserted.
+      properties:
+         - name: SensorValue
+           type: double
+           description: >
+               The sensor value that triggered the alarm change.
+    - name: CriticalLowAlarmAsserted
+      description: >
+          The low threshold alarm asserted.
+      properties:
+         - name: SensorValue
+           type: double
+           description: >
+               The sensor value that triggered the alarm change.
+    - name: CriticalLowAlarmDeasserted
+      description: >
+          The low threshold alarm deasserted.
+      properties:
+         - name: SensorValue
+           type: double
+           description: >
+               The sensor value that triggered the alarm change.