Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Patent
1997-01-21
1999-03-09
Negash, Kinfe-Michael
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
359172, 370310, H04B 1000
Patent
active
058808671
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is a U.S. national stage entry of PCT Application PCT/US96/04396 (Attorney Docket Nos. 10522WO02 & DN38066X PCT), filed Mar. 29, 1996, having priority based upon U.S. application Ser. No. 08/415,063 (Attorney Docket No. DN38066X), filed Mar. 29, 1995.
BACKGROUND OF THE INVENTION
The present invention relates generally to a communication network used to maintain communication exchanges within an enclosed premises; and, more particularly, it relates to a method and apparatus for maintaining communication exchanges utilizing both infrared and radio frequency transmissions in a premises such as an office building, hospital, factory floor, or the like.
As is well known, radio frequency (RF) transmissions have been used to maintain point to point communication. However, use of RF transmissions in a premises can cause several problems. For example, RF transmissions can interfere with the proper functioning of other equipment in the premises. Such interference is particularly undesirable in a premises such as a hospital, where the equipment may provide life support to patients. Further, because the Federal Communication Commission (FCC) has allocated only certain frequencies to premises RF communication networks, interference may also occur between adjacent premises. Thus, RF communication in a premises may be hindered by RF noise from surrounding premises. Such noise may become a significant burden to communication in a premises located in a crowded, city environment.
These interference problems may also be enhanced given the physical layout of most premises. Specifically, a typical premises comprises structural supports and walls which limit the penetration of RF transmission. If the transmission power is too low, certain areas may arise wherein RF transmissions cannot be received (i.e., "dead zones"). While increasing the RF transmission power may increase penetration and eliminate dead zones, it also increases the likelihood that the above-described interference problems may occur.
In addition, increasing the RF transmission power may also be undesirable for health reasons. Specifically, it has been alleged that RF transmissions may potentially cause damage to human tissue or cells, and thus may be carcinogenic. As a result, it may be desirable to not only limit the RF transmission power in a premises, but also limit the use of RF transmissions altogether.
As is also well known, modulated infrared light has also been used to maintain point to point communication. Use of infrared light as such in a premises is a desirable alternative to RF transmissions because infrared light is rather harmless to humans and does not cause the interference problems discussed above. However, use of infrared light for communication in a premises causes a unique set of problems. For example, infrared communication is limited in range because it is directional, i.e., it requires "line of sight" type transmissions. As a result, it is difficult to provide communication over an entire premises using only infrared transmissions. In addition, dead zones are created easily in infrared systems by mere interruption of the light stream, resulting in a loss of data.
While infrared systems are less expensive than those using RF, they are not a viable alternative to RF because of these problems. Infrared communication has had virtually no market use in mobile environments, and has only been a solution to replacing RS232 and parallel wiring in short distance, line of sight environments such as between a personal computer and associated input and output devices (e.g., keyboard, mouse, printer, etc.).
In airplanes, the use of electronic equipment is permitted but with many restrictions. For example, during take off and landing, all such equipment must be turned off to prevent unintentional yet often inherent RF transmissions from interfering with cockpit electronics. Such interference proves annoying yet is tolerated by cockpit crews during the less critical period between take o
REFERENCES:
patent: 5034997 (1991-07-01), Iwasaki
patent: 5301353 (1994-04-01), Borras et al.
patent: 5424859 (1995-06-01), Uehara et al.
Intermec IP Corp.
Negash Kinfe-Michael
LandOfFree
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