Question

When the administrative information is transmitted by Infrared Communication, the leakage of it is the serious cause of anxiety. There is not the detail explanation about the security in your home page. I want to know the technical explanation why there is no leakage.

Answer

When the administrative information is transmitted, we must examine both of the transmission method and the physical layout.

(A)	The transmission method of the information is supposed as follows.
	(a)	Cable Communication of metal wire or optical fiber
	(b)	Radio Wave Communication
	(c)	Infrared Communication
(B)		The physical layout (topology) is supposed as follows.
	(a)	Point to Point (P-P) : Connection of center and repeater, for example the entrance link
	(b)	Point to Multi-Point (P-MP) : Connection of HUB and plural nodes, for example LAN

When the combination of (A) and (B) is examined, the examination points are the simplicity of setup, the communication speed, the reliability and the security.

The topology of Infrared Communication is as follows.

1. P-P : Outdoor Communication between equipments 1〜2km apart
2. P-MP : Indoor Communication between HUB and plural nodes in 10m radius area

The reason of the high security is different respectively.

In the case of (1), the high security is maintained because the laser beam has the sharp directivity different from radio wave and the beam axis must be coincident with each other for the normal communication.

Infrared Communication transmits the concentrated beam to the opposite equipment. Illegal receiver can be detected because it must be setup on the communication route for the tap and the beam axis adjustment is also needed. In the case of Radio Wave Communication, there is the side lobe component from antenna and the radio wave beam is not so sharp as Infrared. The tap is difficult in the case of Infrared Communication.

In the case of (2), the high security is maintained because the beam can not pass through the wall for the communication between HUB and plural nodes. The signal does not leak from the room.

The above explanation is for the security against the illegal reception in the free space. But the security level of the electrical signal converted from Infrared is the same as optical fiber and radio wave.