Background of the Invention Contemporary vehicles are often equipped with alarm systems, emergency telephone systems and the like. One purpose of these systems is to track the position of the vehicle once the vehicle has been identified as being stolen.

A problem with conventional systems is that audible ringing for incoming telephone calls is not suppressed.

What is needed is an improved approach for handling incoming telephone calls originated from the emergency response center so that the vehicle's occupants are not signaled in case of an emergency telephone call especially when the vehicle position is being tracked in case the vehicle is stolen.

Brief Description of the Drawings FIG. 1 is a block diagram of an emergency telephone system in accordance with a preferred embodiment of the invention; and FIG. 2 is a flow chart showing a preferred method of the emergency telephone system ring suppressor.

Detailed Description of a Preferred Embodiment An apparatus and method of ring suppression in an emergency telephone system includes receiving an incoming telephone call.

Audible signaling conventionally associated with receipt of the incoming telephone call is suppressed if it is determined that the incoming telephone call originated from an emergency response center.

Preferably, when telephone call is received from the emergency response center, then communicate the vehicle's position.

FIG. 1 is a block diagram of an emergency telephone system in accordance with a preferred embodiment of the invention. A vehicle mounted emergency telephone system 100 includes a controller 101 preferably constructed using a single chip microcontroller such as a Motorola MC68HC05 microcontroller. The Motorola MC68HC05 microcontroller has on-board program memory used to store the portion of the preferred method described later. The MC68HC05 microcontroller also has a built-in electrically erasable programmable read only memory (EEPROM). Those skilled in the art will readily recognize that other microcontrollers and hardware logic circuits may be substituted for the MC68HC05 microcontroller.

The controller is connected between a handset 103 and a mobile radiotelephone 105. A Global Positioning System (GPS) receiver 107, and optionally a hands-free speaker 111 are also operatively coupled to the controller 101.

The handset 103 has an audio transducer, here a speaker 109 used to signal ringing as well as communicate a vocal conversation. The handset may also have a separate audio transducer used to signal ringing. Note that the hands-free speaker 111 can also be used to signal an incoming call to the vehicle's operator and communicate a vocal conversation as well. The GPS receiver 107 enables the emergency telephone system 100 to keep track of the position of the vehicle. This

is important when an emergency occurs because the vehicle's position can be communicated to the emergency response center. Of course other position determinations means can be substituted for the GPS receiver 107.

The mobile radiotelephone 105 portion of the emergency telephone system 100 can receive a telephone call initiated from another radiotelephone 113, via a radiotelephone infrastructure site 115, or from an emergency response center 117. The mobile radiotelephone 105 will receive a telephone call initiated via the radiotelephone infrastructure site 115 when some one intends to call the vehicle's operator to have a voice conversation. The mobile radiotelephone 105 will receive a telephone call initiated from the emergency response center 117 during a special situation, such as when the vehicle is known to be stolen. Telephone calls from the emergency response center 117 will typically be data rather than voice calls.

Now that the system hardware has been described, the preferred method will be detailed. FIG. 2 is a flow chart showing a preferred method of the emergency telephone system ring suppressor. The method steps described here are encoded into the earlier described controller 101, introduced in FIG. 1. In a first step 201, the emergency telephone system 100 waits for an incoming call notification. The incoming call can originate either from the emergency response center 113 or another telephone via a cellular infrastructure.

Next, in step 203, the handset 103 is disconnected from the mobile radiotelephone 105. More specifically any audio transducers such as the speaker 109 are disabled, so the handset 103 will not make a ringing sound which would alert an occupant of the vehicle. One scenario where this would be useful is when the vehicle is reported as stolen and the owner wants to track the position of the vehicle by making a silent call and prompting the emergency telephone system 100 top send the vehicle's position as determined by the on-board GPS receiver 107.

Then, in step 205 the emergency telephone system 100 checks to see if theft recovery was enabled. The theft recovery option is preprogrammed into the EEPROM memory of the controller 101. If the theft recovery option is not enabled, then the method advances to step 213 to wait for a selected period. Then, in step 215 the handset is reconnected to the mobile radiotelephone 105 and the handset is allowed to ring. In this case either the speaker 109 or the hands-free speaker 111 will sound.

If the theft recovery option is enabled, then the method advances to step 207. In step 207 the emergency telephone system 100 answers the incoming telephone call.

Next, in step 209 the controller 101 determines whether or not the incoming telephone call originated from the emergency response center 117. If the incoming telephone call originated from the emergency response center 117, then the incoming call is processed in step 217. If the incoming telephone call did not originate from the emergency response center 117, then it must be a call originating from the radiotelephone infrastructure site 115 and the audio functions of the handset and the hands-free speaker 111 are reconnected to the mobile radiotelephone 105 via the controller 101 and a pseudo, or substitute ringing sound is sounded through the speaker 109 and/or the hands-free speaker 111. The method then repeats.

An improved approach for handling incoming telephone calls has been detailed. Telephone calls originating from the emergency response center do not audibly ring through and alert the vehicle's occupants in case of an emergency telephone call especially when the vehicle position is being tracked in case the vehicle is stolen.