diff --git a/c_os/devices/PCSPK.h b/c_os/devices/PCSPK.h
index c6d0fba..d71e220 100755
--- a/c_os/devices/PCSPK.h
+++ b/c_os/devices/PCSPK.h
@@ -78,7 +78,7 @@ public:
     void aerodynamic();
 
     // Ton abspielen
-    void play(float f, int len);
+    static void play(float f, int len);
 
     // Lautsprecher ausschalten
     static void off();