BRIEF DESCRIPTION OF THE DRAWINGS
The invention, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:
FIG. 1 is a block diagram showing a construction of a security system according to a first embodiment of the present invention;
FIG. 2 is a block diagram showing a construction of a security system according to a second embodiment of the present invention; and
FIG. 3 is a schematic plan view showing a house and its premises in which a security system is installed according to a third embodiment of the present invention.