Abstract: A vibration sensor device is mounted on a translucent ornamental disc so it can be mounted at any desired position on a window pane so as to achieve the greatest sensitivity without being asthetically offensive. A bracket affixed to the disc mounts a base to which electrical leads are attached to connect the sensor to an alarm control unit. A motion sensing switch is detachably connected to the base to allow easy substitution of switches of different sensitivities. A cover hides the bracket, base, and switch and the whole unit is adhesively attached to the window pane.