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10
DESIGNING A SYSTEM
Designing an intrusion and security alarm system using battery-powered radio devices is
easy, provided that you follow some simple instructions. A good design ensures easy
installation and proper functioning of the system. This chapter provides all of the
information required to reach these objectives.
10.1
Information on radio waves
The systems that use radio waves to connect devices offer the significant benefit of being
able to install and connect the various pieces of equipment without needing to perform
complex wiring operations. One disadvantage is that greater care is required when
positioning the devices, in order to obtain the best radio connection.
The quality of a radio connection is directly proportional to the power of the signal that
reaches the device. This power is affected by the distance between the devices (the power of
the radio signal decreases with each square of distance) and any signal absorption
phenomena caused by obstacles along the radio wave route.
Remaining power after
crossing
Material crossed
90-100%
Wooden or plastic furniture, synthetic materials (e.g. plexiglass), glass,
perforated bricks, plasterboard
65-85%
Solid bricks, marble, fish tanks
10-60%
Reinforced concrete, metal structures (household appliances, pipes, railings)
0-10%
Metal sheets, mirrors
