Radio telephone system

• US 4,939,766 A
• Filed: 07/08/1988
• Issued: 07/03/1990
• Est. Priority Date: 07/10/1987
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Sasaki, Isao, Umemoto, Yuji
• Primary Examiner(s): Lev, Robert
• Application Number:
  US07/216,688
• Time in Patent Office: 725 Days
• Field of Search: 379/58, 379/1, 379/63, 455/69, 455/33
• US Class Current: 455/462
• CPC Class Codes: H04M 1/72508 using a control channel

Abstract

A radio telephone system comprises a base unit electrically connected to a wire telephone line and at least one radio telephone set which can be connected to the base unit through a radio communication line. A predetermined threshold value is normally set for the intensity of a received electric field generated in the radio line so that, when the received electric field intensity does not reach the threshold value, for example when the radio telephone set is separated by more than a predetermined distance from the base unit, the radio communication line is automatically cut off. In the radio telephone system, the threshold value for the received electric field intensity can be arbitrarily modified by means of a suitable operating member disposed in the radio telephone set to thereby increase the flexibility of the radio telephone system. The operating member can comprise, of course, an exclusive key switch, a pushbutton switch or the like, or alternatively a dial key or the like previously provided in the radio telephone set may be commonly used also as the operating member.

Claims

1. A radio telephone system comprising:

base unit means connected to a wire telephone line;

telephone set means having dial means, transmitter means and receiver means; and

radio control means for controlling interconnection between said base unit means and said telephone set means through a radio line, said radio control means comprising;

detection means for detecting a received intensity of an electric field received through said radio line by comparing an actually received electric field intensity with a selected one a plurality of set threshold values for the field intensity;

control circuit means for maintaining an interconnection mode through said radio line when said detection means detects that said received electric field intensity is larger than said selected threshold value; and

an operating member for selecting an arbitrary one of said plurality of set threshold values according to an arbitrary manipulation by an operator;

wherein said detection means, said control circuit means and said operating member are disposed in said radio control means of said telephone system, said radio control means being located in said telephone set means; and

wherein said set threshold values of said detection means include a first threshold value corresponding to a first value of said received electric field intensity and a second threshold value corresponding to a second value smaller than said first value, and said detection means selects said first threshold value when said operating member is not operated and said second threshold value when said operating member is operated.

2. A radio telephone system according to claim 1, wherein said first value corresponds to a received electric field intensity of 20 dbμ

V and said second value corresponds to a received electric field intensity of 10 dBμ

V.

3. A radio telephone system according to claim 1, wherein said first value corresponds to an electric field intensity of 20 dBμ

V and said second value corresponds to a received electric field intensity of 0 dBμ

V.

4. A radio telephone system according to claim 1, wherein said detection means enables selection and modification of said threshold values on the basis of logical product conditions that said radio line is in a completed interconnection state and that said operating member is completely operated.

5. A radio telephone system according to claim 1, wherein said detection means further includes a timer circuit which has a set predetermined timer time, and passage of said predetermined timer time after the selection and modification of said threshold value causes the threshold value to be automatically returned to said first value.

6. A radio telephone system according to claim 1, wherein said operating member is used as said dial means of said telephone set means.

7. A radio telephone system comprising:

base unit means connected to a wire telephone line;

telephone set means having dial means, transmitter means and receiver means; and

radio control means for controlling interconnection between said base unit means and said telephone set means through a radio line, said radio control means comprising;

detection means for detecting a received intensity of an electric field received through said radio line by comparing an actually received electric field intensity with a selected one of a plurality of set threshold values for the field intensity;

control circuit means for maintaining an interconnection mode through said radio line when said detection means detects that said received electric field intensity is larger than said selected threshold value; and

an operating member for selecting an arbitrary one of said plurality of set threshold values according to an arbitrary manipulation by an operator;

wherein said detection means, said control circuit means and said operating member are disposed in said radio control means of said telephone system, said radio control means being located in said telephone set means; and

wherein said detection means continuously presets as said set threshold values, values ranging from a first value of said received electric field intensity to a second value smaller than the first value, and selects said first value when said operating member is not operated and sequentially selects one of said values close to said second value when said operating member is operated in response to an operation amount of said operating member.

8. A radio telephone system according to claim 7, wherein said first value corresponds to a received electric field intensity of 20 dBμ

V and said second value corresponds to a received electric field intensity of 10 dBμ

V.

9. A radio telephone system according to claim 7, wherein said first value corresponds to a received electric field intensity of 20 dBμ

V and said second value corresponds to a received electric field intensity of 0 dBμ

V.

10. A radio telephone system according to claim 7, wherein said detection means enables selection and modification of said threshold values on the basis of logical product conditions that said radio line is in a completed interconnection state and that said operating member is completely operated.

11. A radio telephone system according to claim 7, wherein said detection means further includes a timer circuit which has a set predetermined timer time, and passage of said predetermined timer time after the selection and modification of said threshold value causes the threshold value to be automatically returned to said first value.

12. A radio telephone system comprising:

base unit means connected to a wire telephone line;

telephone set means having dial means, transmitter means and receiver means; and

radio control means for controlling interconnection between said base unit means and said telephone set means through a radio line, said radio control means comprising;

detection means for detecting a received intensity of an electric field received through said radio line by comparing an actually received electric field intensity with a selected one of a plurality of set threshold values for the field intensity;

control circuit means for maintaining an interconnection mode through said radio line when said detection means detects that said received electric field intensity is larger than said selected threshold value; and

an operating member for selecting an arbitrary one of said plurality of set threshold values according to an arbitrary manipulation by an operator;

wherein said detection means, said control circuit means and said operating member are disposed in said radio control means of said telephone system, said radio control means being located in said telephone set means; and

wherein said detection means stepwise presets as said set threshold values, values ranging from a first value of said received electric field intensity to a second value smaller than the first value, and selects said first value when said operating member is not operated and sequentially selects one of said values close to said second value when said operating member is operated in response to an operation amount of said operating member.

13. A radio telephone system according to claim 12, wherein said first value corresponds to a received electric field intensity of 20 dBμ

V and said second value corresponds to a received electric field intensity of 10 dBμ

V.

14. A radio telephone system according to claim 12, wherein said first value corresponds to a received electric field intensity of 20 dBμ

V and said second value corresponds to a received field intensity of 0 dBμ

V.

15. A radio telephone system according to claim 12, wherein said detection means enables selection and modification of said threshold values on the basis of logical product conditions that said radio line is in a completed interconnection state and that said operating member is completely operated.

16. A radio telephone system according to claim 12, wherein said detection means further includes a timer circuit which has a set predetermined timer time, and passage of said predetermined timer time after the selection and modification of said threshold value causes the threshold value to be automatically returned to said first value.

17. A radio telephone system comprising:

base unit means connected to a wire telephone line;

telephone set means having dial means, and transmitter means and receiver means; and

radio control means for controlling interconnection between said base unit means and said telephone set means through a radio line, said radio control means comprising;

detection means for detecting a received intensity of an electric field received through said radio line by comparing an actually received electric field intensity with a selected one of a plurality of set threshold values for the field intensity;

control circuit means for maintaining an interconnection mode through said radio line when said detection means detects that said received electric field intensity is larger than said selected threshold value; and

an operating member for selecting an arbitrary one of said plurality of set threshold values according to an arbitrary manipulation by an operator;

wherein said detection means, said control circuit means and said operating member are disposed in said radio control means of said telephone system, said radio control means being located in said telephone set means; and

wherein said operating member is used as said dial means of said telephone set means, said detection means stepwise presets as said set threshold values, values ranging from a first value of said received electric field intensity to a second value smaller than the first value, and selects said first value when said dial means is not operated and selects a different one of said values other than the first value when the dial means is operated in response to dial information.

18. A radio telephone system according to claim 17, wherein said first value corresponds to a received electric field intensity of 20 dBμ

V and said second value corresponds to a received electric field intensity of 10 dBμ

V.

19. A radio telephone system according to claim 17, wherein said first value corresponds to an electric field intensity of 20 dBμ

V and said second value corresponds to a received electric field intensity of 0 dBμ

V.

20. A radio telephone system according to claim 17, wherein said detection means enables selection and modification of said threshold values on the basis of logical product conditions that said radio line is in a completed interconnection state and that said operating member is completely operated.

21. A radio telephone system according to claim 17, wherein said detection means further includes a timer circuit which has a set predetermined timer time, and passage of said predetermined timer time after the selection and modification of said threshold value causes the threshold value to be automatically returned to said first value.

22. A radio telephone system comprising:

a base unit means connected to a wire telephone line;

telephone set means having dial means, transmitter means and receiver means; and

radio control means for controlling interconnection between said base unit means and said telephone set means through a radio line, said radio control means comprising;

detection means for detecting a received intensity of an electric field received through said radio line by comparing the actually received electric field intensity with a selected one of a plurality of set threshold values for the field intensity;

control circuit means for maintaining an interconnection mode through said radio line when said detection means detects that said received electric field intensity is larger than said selected threshold value; and

an operating member for selecting an arbitrary one of said plurality of set threshold values according to an arbitrary manipulation by an operator;

wherein said detection means and said control circuit means are disposed in both of said radio control means on the side of said base unit means and said radio control means on the side of said telephone set means and said operating member is disposed in the radio control means on the side of the telephone set means so that the operation information of the operating member is transmitted to the radio control means of the base unit means through said radio line.

23. A radio telephone system comprising:

base unit means connected to a wire telephone line;

telephone set means having dial means, transmitter means and receiver means; and

radio control means for controlling interconnection between said base unit means and said telephone set means through a radio line, said radio control means comprising;

detection means for detecting a received intensity of an electric field received through said radio line by comparing an actually received electric field intensity with a selected one of a plurality of set threshold values for the field intensity;

control circuit means for maintaining an interconnection mode through said radio line when said detection means detects that said received electric field intensity is larger than said selected threshold value and for terminating said interconnection mode when said detection means detects that said received electric field intensity is less than said selected threshold value; and

an operating member for selecting an arbitrary one of said plurality of set threshold values according to an arbitrary manipulation by an operator and for changing the threshold value at which said interconnection mode is terminated;

wherein said detection means, said control circuit means and said operating member are disposed in said radio control means of said telephone system.

24. A radio telephone system having a base unit connected to a wire telephone line and a telephone set selectively coupled to said base unit via a radio link, comprising:

establishing means for establishing the radio link between said base unit and said telephone set;

measuring means coupled to said establishing means for measuring a field intensity of signals transmitted over the established radio link;

setting means for setting a threshold level which is variable in response to a user'"'"'s operation;

comparing means coupled to said measuring means and said setting means for comparing the measured field intensity with the threshold level;

maintaining means responsive to said comparing means for maintaining the established radio link if the level of the measured field intensity is above the threshold level, the threshold level being set by said setting means in response to the user'"'"'s operation so as to maintain the established radio link; and

terminating means responsive to said comparing means for terminating said established radio link if the level of the measured field intensity is below the threshold level set by said setting means as a termination level.

25. The radio telephone system according to claim 24, further comprising:

indicator means coupled to said comparing means for providing an indication to a user of the system when the measured field intensity decreases below a predetermined level.

26. The radio telephone system according to claim 24, wherein said maintaining means fails to maintain the established radio link on the condition that the measured field intensity has been below the threshold for a predetermined time period.

27. A method for continuing to maintain an established radio link for use in a radio telephone system, comprising the steps of:

measuring a level of a field intensity of signals transmitted over the established radio link;

setting a threshold level to a first level, the threshold level to be compared with the level of the measured field intensity;

maintaining the established radio link while the measured field intensity is equal to or above the first level;

changing the threshold level to a second level which is lower than the first level in response to a user'"'"'s operation; and

continuing to maintain the established radio link after the measured field intensity decreases below the first level if the measured field intensity is above the second level.

28. The method according to claim 27, further comprising the step of alarming a user of the system in the event that the measured field intensity decreases below a predetermined level.

29. The method according to claim 27, further comprising the step of terminating the established radio link in the event that the measured field intensity has been below the second level for a predetermined time period.