Telecommunications – Radiotelephone system – Security or fraud prevention
Reexamination Certificate
1998-07-28
2001-04-10
Cumming, William (Department: 2684)
Telecommunications
Radiotelephone system
Security or fraud prevention
C370S465000
Reexamination Certificate
active
06215991
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of changing the code of a radio communication system, and more particularly to such a method which achieves the change of the code of a radio communication system through a gap between channels.
2. Description of the Prior Art
In a wireless telephone, a particular code is set for communication between the base and the hand set to prevent others from using the line unlawfully. However, because the code of a wireless telephone can easily be decoded by conventional techniques, the code must be regularly changed. Theexposure of the code of a wireless telephone to the public invites good-for-nothing persons to use the line without payment, and the wireless telephone owner will receive a high amount of debit note from the telephone (exchange) company. In order to protect a wireless telephone from being used unlawfully, the set code of the wireless telephone must be regularly changed. Even if the set code of the telephone line is decoded by an intruder, the intruder can only use the line unlawfully for a short period of time if the wireless telephone owner frequently changes the set code. Conventionally, there are two methods used for changing the code of a wireless telephone. One is achieved by means of charging terminals, i.e., the code is changed by means of the battery charger when the hand set is put back and attached to the base. It is necessary to attach switch means
12
;
15
to the base and the hand set when using charging terminals
11
and battery charger
11
. When charging, the switch means
12
;
15
are respectively switched to the charging circuit
13
and the battery
16
. When changing the code, the switch means
12
;
15
are respectively switched to the microcontrollers
5
;
1
. However, because the signal for charge charging and the signal for code changing are different, it is complicated to design the switch means
12
;
15
, and a software must be provided subject to a communication protocol for support. Therefore, this method is not economic. The other method is achieved by means the hardware of the base and the hand set. This method is less expensive, however it interferes with the communication signal in the channel under use when changing the code. In a regular 25-channel 46/48 MHz wireless telephone, the changing of the set code is achieved through the transmitting frequency of 43.72 MHz~46.97 MHz at the base and the transmitting frequency of 48.76 MHz~49.99 MHz at the hand set. However, because the 25 channels of the wireless telephone are of regular communication channels, using one of the 25 channels to change the set code may: (1) interfere with the communication of the subscriber's telephone, (2) cause a code change failure, and/or (3) cause a communication failure between the base and the hand set due to different codes.
SUMMARY OF THE INVENTION
The present invention has been accomplished to provide a method of changing the code of a radio communication system which eliminates the aforesaid problems. The method of changing the code of a radio communication system having a main unit and a remote unit, includes the steps of: (1) setting the communication frequency of the main unit of the radio communication system at the gap between a first channel and a second channel of the main unit, (2) setting the communication frequency of the ot unit at the gap between a first channel and a second channel of the remote unit, and (3) changing the set code after setting of the communication frequency of the main unit and the communication frequency of the remote unit. The communication frequency of the main unit is the transmitting frequency of the main unit, and is set at the gap between the first channel and the second channel of the main unit through a frequency selector mounted in the main unit. According to one embodiment of the present invention, the frequency of the first channel of the main unit in 46.87 MHz, the frequency of the second channel of the main unit is 46.93 MHz, and the transmitting frequency set by the frequency selector of the main unit is 46.90 MHz. The radio communication system can be a wireless telephone. The transmitting frequency of the remote unit is the transmitting frequency of the remote unit, and is set at the gap between the first channel and the second channel of the remote unit through a frequency selector mounted in the remote unit. The frequency of the first channel of the remote unit is 49.93 MHz, the frequency of the second channel of the remote unit is 49.97 MHz, and the tramsmitting frequency set by the frequency selector of the remote unit is 49.95 MHz. The main unit of the radio communication system is controlled to: (a) confirm that the remote unit has been put back to the main unit, (b) send a recognition signal to the remote unit upon receipt of a code change request signal from the remote unit, (c) receive a new code from the remote unit, (d) send a new code to the remote unit, and (e) receive a recognition signal from the remote unit after dispatch of the new code to the remote unit. The remote unit of the radio communication system is put back to the main unit, and then controlled to: (a) send a code change request signal to the main unit, (b) send a new code to the main unit upon receipt of a recognition signal from the main unit, (c) receive the new code from the main unit, and, (d) send a recognition signal to the main unit upon receipt of the new code from the main unit.
REFERENCES:
patent: 5995515 (1999-11-01), Suzuki
Chen Tien-En
Mou Michael
Cumming William
Dbtel Incorporated
Rosenberg , Klein & Lee
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