The four different functions, horn, engine noise, flashing lights and siren sounds can be activated by pressing the button. The function is immediately turned off by repeatedly pressing the button. The automatic switch-off function is activated after approx. 18 seconds. 2 AAA batteries included. The siren sound can also be switched from the American to the European version with a switch in the battery compartment. The module is suitable for all MAN and MB Actros trucks and Volvo type Unimog and MB trucks (not included).