Emergency number dialing from a fixed cellular terminal

Details Emergency number dialing from a fixed cellular terminal Emergency number dialing from a fixed cellular terminal

1998-10-19

2001-12-18

Banks-Harold, Marsha D. (Department: 2682)

Telecommunications

Radiotelephone system

Emergency or alarm communication

C455S521000

Reexamination Certificate

active

06332073

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to fixed cellular telephony, and, more specifically, to the area of making an emergency call from a fixed cellular terminal.
BACKGROUND OF THE INVENTION
Since the introduction of emergency number dialing in the 1960's, almost every telephone service provider in almost every country has some form of emergency number. A person can dial the emergency number from virtually any telephone (even a pay phone) and be connected to emergency services. Emergency numbers are selected so that they can be easily recalled and dialed. In the U.S., for example, the number is “911.” In Sweden, the number is “112.”
Emergency number dialing is also practiced in wireless networks. Most wireless stations recognize one or more emergency numbers (911, 999, *999, etc.) and access the wireless network differently than in a regular call. A special emergency message is sent to the wireless system, which causes the wireless system to bypass most or all of the call setup (digit analysis and so forth) and authentication steps commonly performed. A call is immediately set up directly to the public safety answering point. Even a wireless station that is not yet activated can place an emergency call.
Emergency number dialing, however, is not quite as simple or straight forward in a new and rapidly growing sector of the local telephone market. Fixed cellular is becoming the solution of choice for providing telecommunication services for a number of diverse applications. In fixed cellular, one or more standard telephones (sometimes called plain old telephones or “POTS”), facsimile machines, modems, etc. in a home or office are connected via normal premises wiring to a line interface controller and then to a cellular terminal. The cellular terminal provides service for the fixed cellular telephones through the air interface of a cellular communications system, just like any other cellular communication device.
Telecommunications providers attempting to enter the local service market use fixed cellular to serve a number of customer premises with a minimal investment in infrastructure. The cost of running wire through the entire area to serve a few customers is avoided. More importantly, erecting a few cellular towers and installing a little customer premise equipment may rapidly develop areas that did not formerly have telephone service at all.
As stated above, the telephones in fixed cellular systems are essentially identical to those used in wireline service. In fixed cellular systems, however, the steps for placing a call are slightly different. Generally, there are three approaches in common usage for placing a call in the fixed cellular environment: send key dialing, timeout dialing and digit-by-digit dialing.
Send key dialing is similar to the standard operation of a mobile telephone. At the conclusion of entering the destination telephone number, the user presses a predefined key on the telephone to instruct the fixed wireless system to send the call to the wireless network. The send key is usually the “#” or “★” key on a standard telephone keypad. Once the call is finally sent to the wireless network, it receives the same priority and processing as any other emergency access. However, if the user forgets to dial the send key (not a common operation to people conditioned to normal landline dialing, especially in an emergency), the emergency call will never be sent.
In timeout dialing, the fixed cellular service attempts to analyze the dialed digits to determine the last number dialed by the subscriber so that the user does not have to press a send key. If a timer expires without any keys being pressed (typically 3-5 seconds from the last number dialed) the digits are sent to the wireless network to set up a call. In emergencies, the user must wait for the Umeout, usually without any audible feedback from the telephone. In an emergency, a user may become confused after dialing the emergency number and perhaps think that the call did not go through. If the user hangs up and tries again, the delay of call completion increases.
Digit-by-digit dialing automatically places a cellular call to a predefined telephone number at the mobile switching system (sometimes called a “roamer port”) as soon as the user starts dialing. The dialed digits are collected and transmitted to the mobile switching system for analysis and call connection. The cellular system does not recognize the access as an emergency, since the first part of the cellular access is to the roamer port. Further, the mobile station to cellular network interaction is no different from any other call. If the serial number checking or authentication fail during the access, then the call is not completed at all.
SUMMARY OF THE INVENTION
According to one aspect of this invention, a method is disclosed for use in a fixed cellular terminal for screening outgoing calls for an emergency number. The emergency number comprises a predefined string of digits. The method comprises the steps of (a) receiving a first dialed digit, (b) comparing the first dialed digit to the first digit of the emergency number, and (c) if the first dialed digit matches the first digit of the emergency number, receiving a next dialed digit. The method further includes the steps of (d) comparing the next dialed digit to the next digit of the emergency number, (e) repeating step (d) until either the next dialed digit does not match the next digit of the emergency number or the dialed digits match all of the plurality of digits of the emergency number and (f) if all of the dialed digits matched all of the plurality of digits of the emergency number, an emergency cellular call is set up.
In accordance with a preferred form of this aspect of the invention, the step of setting up an emergency cellular call includes bypassing normal cellular call set up procedures. In another preferred form of this invention, there is a plurality of emergency numbers and, in a further preferred form, step (b) comprises comparing the first dialed digit to the first digit of each of the plurality of emergency numbers, and step (d) comprises comparing the next dialed digit to the next digit of each of the plurality of emergency numbers. According to a further form of this aspect of the invention, step (e) comprises repeating steps (d) and (e) until the dialed digits match all of the digits of one of the plurality of emergency numbers, or one of the dialed digits does not match its corresponding digit in one of the plurality of emergency numbers.
In another aspect of this invention, a cellular unit is provided which is operable in a cellular network that connects a call to a public safety answering point having an emergency number responsive to an emergency message. The cellular unit has an input device for dialing digits and further includes a digit collector adapted to receive each dialed digit, a memory storing an emergency number, a controller adapted to sequentially compare each received dialed digit to the emergency number; and a cellular terminal adapted to send an emergency message to the cellular network responsive to the controller matching all of the received dialed digits to all of the digits of the emergency number.
It is an object of the present invention to provide a fixed cellular terminal that may be reliably used by all people, particularly in emergencies.
It is another object of the present invention to provide a fixed cellular terminal that may be reliably used in emergencies by persons who are unaware that the terminal is cellular.
It is still another object of the present invention to provide a fixed cellular terminal that quickly and reliably connects an emergency call.


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