Fixed cellular communications system

• US 6,591,114 B1
• Filed: 02/24/2000
• Issued: 07/08/2003
• Est. Priority Date: 02/24/2000
• Status: Expired due to Fees

• Current Assignee: Qualicom Systems Incorporated
• Original Assignee: Qualicom Systems Incorporated
• Inventors: Inbody, Jon E.
• Primary Examiner(s): MAUNG, NAY AUNG
• Application Number:
  US09/512,097
• Time in Patent Office: 1,230 Days
• Field of Search: 455/67.1, 455/74.1, 455/423, 455/424, 455/425, 455/426, 455/462, 455/463, 455/464, 455/465, 455/507, 455/509, 455/520, 455/554, 455/555, 455/567, 455/561, 379/156, 379/157, 379/230, 379/231, 379/232, 379/254
• US Class Current: 455/554.1
• CPC Class Codes: H04W 84/16 WPBX [Wireless Private Branch Exchange]

Abstract

A cellular interface unit is disclosed and is used in association with a trunk line of a private branch exchange or a key system unit. The cellular interface unit includes a cellular-type transceiver, a power supply and control circuitry. The cellular-type transceiver is used for mobile-to-mobile telephone calls with remote cellular telephone units and for mobile-to-landline telephone calls with remote landline telephone units. The control circuitry is used to convert signals between the cellular transceiver and the private branch exchange or key system unit so that the transceiver and its interconnected PBX or KSU function appropriately and so that use of the trunk line establishes a cellular telephone call, while resembling a landline telephone call through the PBX or KSU. Included within the control circuitry is call disconnection supervision circuitry that is responsive to the receipt of an end of call signal from the mobile telephone switching office. In response to the receipt of such signal, the call disconnection supervision circuitry causes the private branch exchange or key system unit to deactivate its associated trunk line and tear down the telephone call by monitoring a physical quantity attributable to the transceiver associated with the interface unit and responding to a change in that physical quantity. The power supply provides a source of electrical energy for the cellular transceiver and the control circuitry.

Claims

1. A cellular interface unit for use in association with a trunk line of a private branch exchange, comprising:

a transceiver;

a power supply electrically coupled to the transceiver;

control circuitry electrically coupled to the transceiver and the trunk line, said control circuitry being an interface between said transceiver and said trunk line; and

call disconnection supervision circuitry coupled to said transceiver and responsive to a predetermined change in a physical quantity attributable to said transceiver, said call disconnection supervision circuitry causing said trunk line to be deactivated upon said predetermined change in said physical quantity.

2. The cellular interface unit as defined by claim 1 wherein said predetermined change of said physical quantity is based on a change of said physical quantity from an operative state indicative of said transceiver being in an operating mode to an inoperative state indicative of said transceiver being in a standby mode.

3. The cellular interface unit as defined by claim 2 wherein said inoperative state of said physical quantity exists when said physical quantity has a value associated therewith that is within a window defined as including values between a high threshold value and a low threshold value.

4. The cellular interface unit as defined by claim 3 wherein said call disconnection circuitry is responsive to said physical quantity value being within said window for a predetermined period of time.

5. The cellular interface unit as defined by claim 4 wherein said predetermined period of time is approximately five hundred milliseconds.

6. The cellular interface unit as defined by claim 1 wherein said physical quantity is operating current of said transceiver.

7. The cellular interface unit as defined by claim 1 wherein said physical quantity is power consumed by said transceiver.

8. The cellular interface unit as defined by claim 1 wherein said call disconnection supervision circuitry comprises a window comparator circuit.

9. The cellular interface unit as defined by claim 8 wherein said window comparator circuit comprises a first operational amplifier and a second operational amplifier electrically coupled to the first operational amplifier.

10. The cellular interface unit as defined by claim 9 wherein said first operational amplifier comprises:

an inverting terminal electrically coupled to said transceiver;

a noninverting terminal electrically coupled to a first reference electrical energy source; and

an output terminal;

wherein said second operational amplifier comprises;

an inverting terminal electrically coupled to a second reference electrical energy source;

a noninverting terminal electrically coupled to the output terminal of said first operational amplifier; and

an output terminal; and

wherein said call disconnection supervision circuit further comprises;

a one-shot device having an input terminal electrically coupled to the output terminal of said second operational amplifer, and an output terminal electrically coupled to said trunk line.

11. A fixed cellular communications system, comprising:

a private branch exchange;

a key set electrically coupled to the private branch exchange;

a trunk line electrically coupled to the private branch exchange;

a cellular interface unit electrically coupled to the trunk line, the cellular interface unit comprising;

a transceiver;

a power supply electrically coupled to the transceiver;

control circuitry electrically coupled to the transceiver and the trunk line, said control circuitry being an interface between said transceiver and said trunk line; and

call disconnection supervision circuitry coupled to said transceiver and responsive to a predetermined change in a physical quantity attributable to said transceiver, said call disconnection supervision circuitry causing said trunk line to be deactivated upon said predetermined change in said physical quantity;

a mobile telephone switching office in electrical communication with the transceiver of said cellular interface unit; and

a mobile transceiver in electrical communication with said mobile telephone switching office.

12. The fixed cellular communications system as defined by claim 11 wherein said private branch exchange is a key system unit.

13. The cellular interface unit as defined by claim 11 wherein said predetermined change of said physical quantity is based on a change of said physical quantity from an operative state indicative of said transceiver being in an operating mode to an inoperative state indicative of said transceiver being in a standby mode.

14. The cellular interface unit as defined by claim 13 wherein said inoperative state of said physical quantity exists when said physical quantity has a value associated therewith that is within a window defined as including values between a high threshold value and a low threshold value.

15. The cellular interface unit as defined by claim 14 wherein said call disconnection circuitry is responsive to said physical quantity value being within said window for a predetermined period of time.

16. The cellular interface unit as defined by claim 15 wherein said predetermined period of time is approximately five hundred milliseconds.

17. The cellular interface unit as defined by claim 11 wherein said physical quantity is operating current of said transceiver.

18. The cellular interface unit as defined by claim 11 wherein said physical quantity is power consumed by said transceiver.

19. The cellular interface unit as defined by claim 11 wherein said call disconnection supervision circuitry comprises a window comparator circuit.

20. The cellular interface unit as defined by claim 19 wherein said window comparator circuit comprises a first operational amplifier and a second operational amplifier electrically coupled to the first operational amplifier.

21. The cellular interface unit as defined by claim 20 wherein said first operational amplifier comprises:

an inverting terminal electrically coupled to said transceiver;

a noninverting terminal electrically coupled to a first reference electrical energy source; and

an output terminal;

wherein said second operational amplifier comprises;

an inverting terminal electrically coupled to a second reference electrical energy source;

a noninverting terminal electrically coupled to the output terminal of said first operational amplifier; and

an output terminal; and

wherein said call disconnection supervision circuit further comprises;

a one-shot device having an input terminal electrically coupled to the output terminal of said second operational amplifer, and an output terminal electrically coupled to said trunk line.

22. A method for using a cellular interface unit electrically coupled with a trunk line of a private branch exchange to control deactivation of said trunk line upon termination of a telephone call, comprising the steps of:

providing a cellular interface unit having a transceiver, a power supply electrically coupled to the transceiver, and control circuitry electrically coupled to the transceiver;

receiving at said transceiver a signal indicative of said termination of said telephone call;

changing a physical quantity attributable to said transceiver in response to receipt of said signal;

detecting said change of said physical quantity; and

causing said trunk line to be deactivated in response to said detection of said change of said physical quantity.