Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1996-12-16
2001-06-05
Trost, William G. (Department: 2681)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S436000, C370S331000
Reexamination Certificate
active
06243583
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a communication system which performs a communication by using a plurality of frequencies.
2. Related Background Art
In recent years, a cordless telephone system has widely been spread and a cordless telephone system of a large scale in which a slaves are dynamically area controlled is being spread.
In such a system, in the case where the slave is moved to another area during the communication and the master connected is switched, a carrier sensing operation or the like is executed and a new communication channel is used.
Since the communication channel is switching as mentioned above, however, a hardware-like instantaneous shut-off time which is required to switch the communication channel (frequency) exists. To reduce such an instantaneous shut-off time, a radio hardware having a high speed synthesizer is used or a plurality of radio units are installed. Such a method results in an increase in costs.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the problem of the conventional system mentioned above.
Another object of the invention is to improve a communication quality.
Still another object of the invention is to provide a cheap communication system of a high communication quality.
Further another object of the invention is to prevent that the communication is instantaneously shut off when the slave is moved to another area.
Further another object of the invention is to provide a communication system in which after the master that is connected to the slave through either one of a plurality of frequencies was switched, the frequency used before the master is switched is also used after completion of the switching.
Further another object of the invention is to provide a communication system in which either one of a plurality of masters and the slaves can be connected through a plurality of communication channels of different frequencies and each of the plurality of communication channels is time-divided to a plurality of communication channels, wherein the case where the master that is connected to the slave is switched, the same communication channel is used before and after the switching.
The above and other objects and features of the present invention will become apparent from the following detailed description and the appended claims with reference to the accompanying drawings.
REFERENCES:
patent: 4718081 (1988-01-01), Brenig
patent: 4759051 (1988-07-01), Han
patent: 5042082 (1991-08-01), Dahlin
patent: 5067147 (1991-11-01), Lee
patent: 5109528 (1992-04-01), Uddenfeldt
patent: 5159593 (1992-10-01), D'Amico et al.
patent: 5175867 (1992-12-01), Wejke et al.
patent: 5210752 (1993-05-01), Ito et al.
patent: 5243598 (1993-09-01), Lee
patent: 5303289 (1994-04-01), Quinn
“Cellular Telephone Technology and Practice” Douglas Kerr. pp. 2:3, 3:3-4, 1994.
Hamada Masashi
Tsutsui Yuichiro
Canon Kabushiki Kaisha
Trost William G.
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