GB2296843A

GB2296843A - Mobile radio station with automatic transmission of an emergency signal

Info

Publication number: GB2296843A
Application number: GB9500167A
Authority: GB
Inventors: Michael Anthony Wilkinson
Original assignee: Motorola Ltd
Current assignee: Motorola Solutions UK Ltd
Priority date: 1995-01-05
Filing date: 1995-01-05
Publication date: 1996-07-10
Anticipated expiration: 2015-01-05
Also published as: GB2296843B; GB9500167D0

Abstract

An emergency or alarm signal is automatically transmitted from a mobile radio station 110 to a system controller 108 in response to a monitoring device 504 sensing a change in impedance of a microphone circuit 124 in the mobile, thereby indicating removal or failure of the microphone 124 or its monitoring device 504. On receiving the emergency signal, the controller 108 may transmit a failure confirmation request to the mobile radio 110. If the controller 108 subsequently receives an acknowledgement from the mobile 110, an equipment failure is reported; if no acknowledgement is received, an emergency situation is assumed. Transmission of an emergency signal caused by disconnection of the microphone 124 due to an attack on the mobile user, eg. a taxi driver, can thus be distinguished from a fault in microphone 124 or in monitoring device 504. The mobile 110 may have an automatic vehicle location (AVL) receiver 126 linked to AVL transmitters 132,134,136, in which case vehicle location information may be transmitted from the mobile 110 with the emergency signal. An alarm on the vehicle may also be activated at the same time. <IMAGE>

Description

MOBILE STATION WITH AUTOMATIC TRANSMISSION OF AN EMERGENCY SIGNAL Field of the Invention This invention relates to a communications system comprising at least one system controller and a number of mobile radio units arranged for communication over a radio communications channel. The invention is applicable to, but not limited to mobile radio equipment having an audio device for providing voice communications to the system controller.

Background of the Invention Radio communications systems exist for mobile applications in which vehicles are equipped with mobile transceivers to allow mobile station users to communicate with base stations, system controllers or other similarly equipped vehicles on the same radio communications system. One such communications system is a dispatch-type radio system where a system controller (dispatcher) transmits messages to, and receives messages from, a number of vehicles in a fleet. Such vehicles are occasionally equipped with Automatic Vehicle Location (AVL) equipment.

Many mobile station users work in professions where they are in danger of being attacked e.g. taxi drivers, fleet company drivers etc.

Typically, in a situation where a mobile station user is being attacked, the mobile station user will neither have the time nor the opportunity to transmit an emergency alarm signal to the system controller. If the mobile station user does attempt to call for help by reaching for the hand-held microphone the attacker will attempt to disconnect or destroy the hand-held microphone, in order to prevent the mobile station user from calling for help.

This invention seeks to mitigate the problem of a mobile station user not being able to transmit an alarm signal to a system controller whilst being attacked.

Summarv of the Invention According to the invention, a mobile station is provided comprising an audio device, e.g. a microphone, for voice communications, operably coupled to monitoring circuitry for monitoring the operation of the audio device. The mobile station further comprises signal generation means for generating an alarm signal indicative of a fault in the audio device when the fault is detected by the monitoring circuitry and a radio transmitter for transmitting the alarm signal.

In this manner, a failure of the audio device monitored by the mobile station causes an alarm signal to be automatically transmitted to the system controller should a mobile station user be attacked and the audio device disconnected.

In a preferred embodiment, the communication signals further include a confirmation request on the nature of the audio device failure, transmitted from the system controller to the mobile station user. On subsequently receiving either no response or receiving further transmissions from the mobile station the system controller determines the nature of the audio device failure.

In this manner, a general failure of the audio device can be distinguished from a case where an audio device is disconnected during an attack on the mobile station user.

Preferably the mobile radio unit will further comprise automatic vehicle location (AVL) equipment for the purpose of generating vehicle location information. When the mobile station user is being attacked the mobile station transmits the vehicle location information together with the alarm signal to the system controller.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the drawings.

Brief Description of the Drawings FIG. 1 shows a block diagram of a known radio communications system in accordance with the preferred embodiment of the invention.

FIG. 2 shows a circuit for monitoring the disconnection or failure of an audio device or its associated circuitry in the mobile station of FIG.

1 according to the preferred embodiment of the invention.

FIG. 3 is a flow diagram illustrating a preferred method for determining the nature of the audio device failure.

Detailed Description of the Drawings Referring first to FIG. 1, a schematic block diagram of a known radio communications system 100 is shown, in accordance with a preferred embodiment of the invention. The radio communications system 100 comprises a system controller i.e. a dispatch sub-system 108, communicating with at least one mobile station 110. According to the preferred embodiment of the invention the radio communications system 100 further comprises an automatic vehicle location (AVL) sub-system 130 for providing vehicle location information to mobile stations having AVL equipment. The operation of AVL systems are well known in the art and need not be described here.

The dispatch sub-system 108 has a dispatch centre 106 connected to a base station 104, in turn connected to an antenna 102 for communicating with the mobile station 110. The mobile station 110 comprises: a transceiver 118 connected to a user interface 122; an audio device 124 connected to an audio device monitoring circuit 504, in turn connected to a signal generating means 116, e.g. a microprocessor for generating alarm signals, and a first antenna 120 for communicating with the dispatch sub-system 108. In the preferred embodiment of the invention the mobile station further comprises an AVL receiver 126 connected to a second antenna 128 for receiving vehicle location information. The AVL sub-system 130 comprises three AVL transmitters 132, 134 and 136 to provide location information to the AVL receiver 126 of the mobile station 110.

Referring now to FIG. 2, a simplified circuit of an audio device and its associated circuitry is shown according to the preferred embodiment of the invention. The audio device 124 has an effective impedance 506 when coupled to the mobile station transceiver 118 and is connected via a two-wire audio device connection 508 to the audio device monitoring circuit 504 of the mobile station 110. The audio device monitoring circuit 504 connects the mobile station transceiver 118 to the audio device 124 and comprises a current monitoring function 500 and an effective output impedance 502.

In operation, the disconnection of the audio device 124 removes the contributory effect of the audio device impedance 506 on the total effective impedance observed across the current monitor. The current measured by the current monitor 500 increases due to the reduction in the total output impedance. The reduction in the total impedance value when a contributing parallel impedance is removed from a circuit is known to one skilled in the art and will not be explained further. The increase in measured current observed by the current monitor 500 causes an automatic alarm signal to be generated by the microprocessor 116 and transmitted from the mobile station 110 to the dispatch centre 106, thereby indicating removal or failure of the audio device 124 or its associated audio device monitoring circuit 504.

Referring now to FIG. 3, a flow diagram is shown illustrating the communications between the dispatch sub-system 108 and the mobile station 110 of FIG. 1, for determining the nature of the audio device failure.

The current monitor 500 effectively monitors the impedance of the audio device 124 and its connection circuit 504 (step 300). When an increase in current is observed (step 302) an alarm signal is generated by the microprocessor 116 and transmitted automatically to the dispatch sub-system 108 from the mobile station 110 (step 304), preferably with vehicle location information provided by the AVL receiver 126. The transmission of AVL information is an optional feature which enhances the effectiveness of the alarm signal.

The dispatch centre 106 registers an audio device circuit failure for the mobile station 110 (step 306) and transmits an audio device failure confirmation request to the mobile station 110 (step 308). If no response is received from the mobile station (step 310), the dispatch centre 106 assumes an "emergency" situation (step 312) and appropriate action is taken at the dispatch centre 106. Alternatively the mobile radio user may transmit further information to the dispatch centre 106 via the user interface 122 confirming that there is a fault with the audio device 124 or its associated circuitry 504 and that no emergency situation exists. An equipment failure is then recorded by the dispatch centre 106 (step 314) and the current monitoring process re-commences once the repair to the audio device 124 or the audio device connection circuit 504 has been made.

In this manner the automatic generation and transmission of an alarm signal caused by the disconnection of the audio device 124 due to an attack on the mobile station user can be distinguished from either a fault in the audio device 124 or its associated audio device connection circuit 504.

As an additional feature, the mobile station 110 can be connected to an alarm system of the vehicle to activate the vehicle alarm at the same time as transmitting the radio alarm signal Thus, this invention provides a useful and effective method of automatically generating and transmitting an alarm signal indicative of the fault to the audio device of a mobile station when the mobile station user is being attacked. In addition the invention offers the benefits of the alarm signal including vehicle location information and the generation of the signal to be initiated by either the mobile station user or an unwitting assailant. The invention advantageously provides a method of communications between the mobile station user and the dispatch centre 106 to confirm the nature of the audio device fault.

Claims

1. A mobile station comprising: an audio device for voice communications, monitoring circuitry for monitoring the operation of the audio device, generation means to generate an alarm signal indicative of a fault in the audio device when the fault is detected by the monitoring circuitry, and a radio transmitter for transmitting the alarm signal.

2. A method of operating a communications system having at least one system controller and a number of mobile stations arranged for communications over a radio channel, the method comprising the steps of: monitoring the operation and failure of the audio device of the mobile station via a monitoring circuit in the mobile station, generating an alarm signal at the mobile station indicative of the audio device failure, transmitting the alarm signal from the mobile station to the system controller, receiving the transmitted alarm signal at the system controller, transmitting a fault confirmation request signal from the system controller to the mobile station, subsequently transmitting from the mobile station to the system controller the nature of the audio device fault, and processing at the system controller of the response or lack of response from the mobile station.

3. A method according to claim 2 wherein subsequent to transmitting a failure confirmation request, the lack of a response from the mobile station is regarded as an emergency signal by the system controller.

4. A method according to claim 2 wherein the alarm signal includes vehicle location information.

5. A communications system comprising at least one system controller and a number of mobile stations arranged for communications over a radio channel, each mobile station comprising: an audio device for voice communications, monitoring circuitry for monitoring the operation of the audio device, generation means to generate an alarm signal indicative of a fault in the audio device when the fault is detected by the monitoring circuitry, transceiver means for communicating the alarm signal to a system controller from the mobile station.