Radio telephone apparatus
First Claim
1. A cellular radiotelephone unit for use in a cellular radiotelephone system for serving one or more geographic areas formed of a plurality of cellular zones, the cellular radiotelephone unit comprising:
- receiving means for receiving radio signals transmitted over a speech radio channel or a control radio channel;
measuring means, coupled to the receiving means, for measuring the strength of the radio signals received by the receiving means;
alarming means for alarming at least the user of the cellular mobile radiotelephone unit in response to the detection of a signal strength value measured by the measuring means at or below a first predetermined value after a communication link with a second party using the speech radio channel is established; and
control means for controlling the receiving means to receive radio signals transmitted over the control radio channel, in stead of the speech radio channel, in response to the detection of a signal strength value measured by the measuring means at or below a second predetermined value, the second predetermined value being no greater than the first predetermined value.
1 Assignment
0 Petitions
Accused Products
Abstract
Radio telephone apparatus for use in a cellular mobile telephone system comprises means for alarming at least a user operating the apparatus in response to a drop in signal strength of radio frequency signals received over an established communication channel when the apparatus approaches a boundary of service area in a cellular mobile telephone system. The signal strength is repetitively checked to determine if it has fallen below a first predetermined signal strength value. When the signal strength falls to or below a second predetermined signal strength value, the radio telephone apparatus causes a disconnection of the telephone link and returns the apparatus to a standby mode.
72 Citations
24 Claims
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1. A cellular radiotelephone unit for use in a cellular radiotelephone system for serving one or more geographic areas formed of a plurality of cellular zones, the cellular radiotelephone unit comprising:
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receiving means for receiving radio signals transmitted over a speech radio channel or a control radio channel; measuring means, coupled to the receiving means, for measuring the strength of the radio signals received by the receiving means; alarming means for alarming at least the user of the cellular mobile radiotelephone unit in response to the detection of a signal strength value measured by the measuring means at or below a first predetermined value after a communication link with a second party using the speech radio channel is established; and control means for controlling the receiving means to receive radio signals transmitted over the control radio channel, in stead of the speech radio channel, in response to the detection of a signal strength value measured by the measuring means at or below a second predetermined value, the second predetermined value being no greater than the first predetermined value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A cellular radiotelephone unit for use in a cellular radiotelephone system for serving one or more geographic areas formed of a plurality of cellular zones, the cellular radiotelephone unit comprising:
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receiving means for receiving radio signals transmitted over a reverse radio channel; broadcasting means for broadcasting radio signals to be transmitted over a forward radio channel; measuring means, coupled to the receiving means, for measuring the strength of the said signals received by the receiving means; alarming means for alarming at least the user of the cellular radiotelephone unit in response to a detection of a signal strength value measured by the measuring means at or below a first predetermined value after a communication link with a second party using the forward and reverse radio channels is established; and control means for controlling the broadcasting means to terminate broadcasting radio signals over the forward radio channel in response to a detection of a signal strength value measured by the measuring means at or below a second predetermined value, not greater than the first predetermined value, the receiving means continuing to receive radio signals transmitted over the reverse radio channel after termination of signal broadcast over the forward radio channel. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A cellular radiotelephone unit of use in a cellular radiotelephone system serving one or more geographic areas formed of a plurality of cellular zones, the cellular radiotelephone unit comprising:
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receiving means for receiving radio signals transmitted over a reverse radio channel; broadcasting means for broadcasting signals to be transmitted over a forward radio channel; measuring means, coupled to the receiving means, for measuring the strength of the signals received by the receiving means; sound generating means for generating sounds and a related sound signal; means for providing the sound signal generated by the sound generating means to the broadcasting means so that the sounds are transmitted to a second party connected to the user of the unit over a communication link using the forward and reverse radio channels in response to the detection of a signal strength value measured by the measuring means at or below a first predetermined value after the communication link is established; and controlling means for controlling the broadcasting means to terminate broadcasting radio signals over the forward radio channel in response to the detection of a signal strength value measured by the measuring means at or below a second predetermined value which is not greater than the first predetermined value after transmitting the sounds to the second party. - View Dependent Claims (18, 19, 20)
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21. A method for alarming a user and a second party connected together over a radio communication link, the method for use in a cellular radiotelephone unit, the method comprising the steps of:
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receiving radio signals transmitted over a control radio and a speech radio channel; broadcasting radio signals to be transmitted over the speech radio channel; measuring the strength of the received radio signals; providing sounds and a related sound signal, the related sound signal being transmitted to the second party in response to the detection of a signal strength value below a first predetermined value after the communication link using the speech radio channel is established; controlling the broadcasting means to terminate broadcasting the radio signals and the receiving means to receive signals transmitted over the control radio channel in stead of the speech radio channel in response to the detection of a signal strength value at or below a second predetermined value after transmitting the related sound signals to the second party. - View Dependent Claims (22, 23, 24)
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Specification