diff --git a/src/main.h b/src/main.h
index a6aeded..ccfd80b 100644
--- a/src/main.h
+++ b/src/main.h
@@ -71,14 +71,14 @@
 extern uint8_t numberWindowsOpen;
 extern uint32_t waitTimeDs;
 extern char textBuf[100];
-extern bool   bRequestShortBeep;
+extern volatile bool   bRequestShortBeep; /* written by loop task, cleared by beepTask */
 extern bool   bIsNightTime;
 extern PiepPattern *piepPattern;
 
-extern DeciSeconds_t tDecis;
+extern volatile DeciSeconds_t tDecis;     /* incremented in timerIsr, read by multiple tasks */
 extern ReceiverFunkThermometerData_t thermoData;
 
-extern uint32_t loopCountSincePause;
+extern volatile uint32_t loopCountSincePause; /* read in pinLevelChangeIsr, written by loop task */
 extern uint8_t toneRequest;
 
 extern Fenster fensterFloBuero;