How to turn off motion detection alarm Homebase 2?

How can I turn off the motion detection alarm on the Homebase 2? I have motion detection turned off on the Doorbell (since I live on a very busy road). When someone rings the bell both the ringtone and the alarm on the Homebase sound. I only want to hear the ringtone. In the settings of the Homebase 2 I can only lower the volume of the alarm, but not turn it off. Thanks!