Telephonic communications – With check operated control – Fraud or interference prevention
Reexamination Certificate
1998-11-04
2001-10-09
Kuntz, Curtis (Department: 2643)
Telephonic communications
With check operated control
Fraud or interference prevention
C379S143000, C379S146000, C379S155000
Reexamination Certificate
active
06301344
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to public telephones and in particular to line powered intelligent pay telephone systems.
BACKGROUND OF THE INVENTION
There is a need for a low cost intelligent public pay telephone. It is desirable that such a telephone be reliable and durable in light of the hostile conditions and environment within which the telephone may have to operate. It is further desirable that this telephone be rich in features that will assure reliable performance.
a) In particular, there is a need to reduce input/output (I/O) pin count circuits used within the present invention for the purpose of incorporating other features requiring I/O reducing cost of circuit functions and improving product reliability.
b) There is a need to reduce microprocessor “bit-banging” (a dedicated CPU-intensive control technique that doesn't allow for simultaneous CPU functionality) when communicating with serial devices used within a telephone system, and to facilitate a reduced-power, high speed method of downloading or uploading pay station data, records, and operating program code, while reducing the product cost and improving product reliability in terms of printed circuit board device interconnections.
c) There is a need to promote software security and to provide a technique of controlling product firmware releases on a per phone basis, to provide unique pay station operation, and to facilitate future firmware or software control on a per phone basis. There is further a need to define a method of controlling firmware configurations.
d) A low power (microamp range), low impedance hook switch interface circuit is needed which is immune to the affects of intruding water, or any other input impedance reducing agent or effect that can cause a false hook switch event or indication. In addition, a method of verifying a circuit oscillator operation (32.768 kHz in this case) in terms of frequency and duty cycle is needed.
e) There is a need to interface the phone chassis with various mechanical coin acceptors that generate a wide range of nickel, dime, and quarter coin pulse widths utilizing a uniform detection algorithm for all coin acceptors. In order to reliably detect the various pulse widths, there exists a need to establish a minimum valid pulse width criteria, and to reject any noise associated for a given coin acceptor mechanism. There is an added need to make coin input filtering less of a CPU intensive function.
f) It is desirable to have a flexible and secure memory page-swapping technique that allows a 64 kbyte direct address range to be expanded, and then be logically repartitioned in a number of segments such that multiple devices in a system can be partitioned in such a way as to not conflict with each other, and further to write-protect all memory on a segment resolution basis.
g) The ability of determining the condition of the phone's primary battery for the purpose of assuring proper phone operation of future battery-dependent functions.
h) There is a need to prevent pin fraud on coin telephone trunk applications.
Pin fraud is a common method of defrauding the telephone. One pin fraud technique includes inserting a fine pin into any one of the four handset interconnect wires within an armored handset cord (provided the interconnect is not ac coupled or isolated in some way) and shorting the pin to the metallic armored cord which is connected to earth ground. This event must take place at the time the central office is performing a local call coin check. Shorting a +5V referenced signal to earth ground will complete the circuit loop, and as a result be interpreted by the central office that the minimum deposit has been satisfied, thereby enabling the call. Another pin fraud technique includes inserting a pin into the armored handset cord as described previously at the time of a post call collect signal application, thereby diverting the collect signal from the escrow relay. Then, upon removing the pin and coming off-hook and going back on-hook, which prompts the central office to send a refund signal to the phone, any money held in escrow from a long distance coin call will be returned instead of collected.
SUMMARY OF INVENTION
In view of the foregoing background, it is therefore an object of the present invention to provide a low cost, high value intelligent pay telephone having proven reliable technology combined with durability and feature rich performance.
These and other objects, features and advantages according to the present invention are provided by an intelligent public telephone system having:
a) AN ADPCM synthesized voice driver using Delta Sigma technology, thereby converting the output pin count from 10 pins to 1 pin, reducing the cost and complexity of voice synthesizer associated circuitry external to an ASIC. The Delta Sigma modulator is a second-order modulator followed by a simple, two-pole, passive filter. The human ear or telephone line serves as the third filter pole.
b) Implemented a single I/O controller circuit in the telephone control ASIC capable of 115 kbps bidirectional data communication. The circuit's protocol is compatible with the slower Dallas Semiconductor one-wire protocol to facilitate a non-bit-banging interface to Dallas Semiconductor devices that incorporate the one-wire design. The one-wire controller is used to provide communications with option board assemblies, future option board assemblies, the resident electronic serial number device, the add-on Firmware Control Key interconnect, future Smart Bezels, future custom ASICs, and for interfacing to product programming and/or data acquisition devices that interface to the pay station product in a hard-wired plug-on fashion, or through a local infrared transceiver interconnection. Again, the solution is implemented by a single wire circuit interconnection tremendously reducing printed circuit board complexity, facilitating product cost reduction through reduced circuitry and facilitating reduced printed circuit board layer count. For these same reasons, the single wire solution improves product reliability.
c) A custom-programmed Dallas Semiconductor DS2502 Electronic Serial Number Device is provided in conjunction with a 3-pin header that will interface with an add-on circuit module, or key. The custom-programmed Dallas device is programmed with a unique code. The device is further programmed by the supplier. To enable future firmware programmed, or to be programmed, into the phone and to be secured, a second uniquely programmed customized Dallas DS2502 device is installed onto the 3-pin header.
An alternate solution is to program a random number, or “seed”, into a customized device, such as the inventor customized Dallas DS2502, or a custom ASIC, by way of example, and to program a unique serial number (S/N) into the phone's non-volatile memory. A firmware algorithm creates a soft “key” based on the ASIC “seed” and the S/N. The “key” will be used to enable future firmware/software programmed, or to be programmed, into the phone and to be secured.
To provide for the security required, three parameters will be implemented. The three parameters include Configuration Code, Product Code, and Revision Level.
d) A hook switch is provided to satisfy the need for low power, low impedance hook switch interface that is immune to the effects of intruding water, by way of example, and the need to verify circuit oscillator operation. The oscillator measurement solution consists of the HKSWclk signal itself, as the 45 &mgr;sec low going pulse represents the 32.768 kHz oscillator frequency period plus the high time portion of the period, while the 125 msec overall HKSWclk signal period represents 4096 times the period of the 32.768 kHz oscillator frequency. Either of these specifications being off would be indicative of which oscillator specification is not correct.
e) A coin detect and debounce circuit is provided that is programmable for minimum pulse width. Pulse widths less than the programmed minimum are ignored. Pulse widths greater than the pro
Bryan Kenneth L.
Felch Raymond F.
Hayes Stephen J.
McBride Tony L.
Meyer Rolf
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Kuntz Curtis
Protel, Inc.
Tran Quoc D.
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