Telephone set having an anti-fraud arrangement which prevents an

Details Telephone set having an anti-fraud arrangement which prevents an Telephone set having an anti-fraud arrangement which prevents an

1997-11-03

1999-01-26

Chiang, Jack

Telephonic communications

Terminal

379145, H04M 1700, H04M 100

Patent

active

058646183

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention concerns a telephone station of the kind set forth in the classifying portion of claim 1.


SUMMARY OF THE INVENTION

The object of the present invention is to propose a telephone station having an anti-fraud arrangement which prevents any fraudulent attempt to telephone from the telephone station without paying the charges which are incurred.
In accordance with the invention that object is attained by the features of claims 1 and 7. Advantageous configurations are set forth in the appendant claims.


BRIEF DESCRIPTION OF THE DRAWING

Embodiments of the invention are described in greater detail hereinafter with reference to the drawing in which:
is FIG. 1 is an electrical diagram of a telephone station connected to a telephone exchange,
FIG. 2 shows a measuring circuit,
FIG. 3 shows a magnetisation curve and signal shapes,
FIG. 4 shows a magnetisation curve and current and voltage configurations, and
FIG. 5 shows a measuring circuit for measuring the input impedance of a transformer.


DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows the electrical circuit diagram of a public telephone station 1 which is connected by way of three lines 2, 3 and 4 to a telephone exchange 5. It has two switches 6 and 7, first and second coils 8 and 9 respectively, a circuit member 10, a measuring coil 11, a body 12 of magnetic material and a measuring circuit 13. The switch 6, the first coil 8, the circuit member 10, the second coil 9 and the switch 7 are electrically connected in series. The switches 6 and 7 are connected on their output sides to the lines 2 and 3 respectively and are actuated by the handset 14 of the telephone station 1. They are opened when the handset 14 is put down and they are closed when the handset 14 is lifted off. The circuit member 10 has two connections which are each connected to the line 4 by way of a respective resistor 15 and 16. The circuit member 10 is the actual core portion of the telephone station 1. From the electrical point of view it represents an impedance Z.sub.T. Further details about the structure of the circuit member 10 are not essential for understanding of the invention and are therefore not described herein.
Within the telephone exchange 5 the first line 2 is connected by way of a coil 17 to an earthed point m, to the line 4 which serves as an earth line, and to a positive terminal of a dc voltage source 18. The second line 3 is connected by way of a coil 19 to the negative terminal of the dc voltage source 18. The telephone exchange 5 has an earthed circuit 20 with a coil 21 and an ac voltage generator 22 which serve inter alia for modulating fee charge pulses onto the two lines 2 and 3. The charge pulses are alternating signals which are generally at a frequency of 50 Hz. The charge pulses are received by the circuit member 10 of the telephone station 1 and are used for example for direct debiting of a credit which has been produced by the insertion of coins or similar payment means. It is also possible that the telephone station 1 firstly adds up the charge pulses and later uses them for billing purposes, for example in the case of cash-less payment by means of a credit card or a chip card.
An electric circuit 23 is connected to the telephone station 1, in the event of intent to defraud. A first feed wire 24 of the circuit 23 is electrically connected to a tapping A of the telephone station 1, which is between the circuit member 10 and the second coil 9. A second feed wire 25 of the circuit 23 is connected to an earthed point m.sub.f. From the electrical point of view the circuit 23 represents an impedance Z.sub.f arranged between the two feed wires 24 and 25. Depending on the kind of fraud involved the circuit 23 can be a telephone or a circuit for weakening the charge pulses.
When the handset 14 is lifted up, a dc circuit is closed: a direct current I.sub.1, flows through the first line 2 from the positive terminal of the dc voltage source 18 by way of the circuit member 10 to the tapping A, a direct current I.sub.2 flows

REFERENCES:
patent: 4759054 (1988-07-01), Mellon
patent: 5022073 (1991-06-01), Jordan
patent: 5086459 (1992-02-01), Perry
patent: 5150403 (1992-09-01), Jordan

Affiliated with

Also associated with

Rating

Telephone set having an anti-fraud arrangement which prevents an does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Telephone set having an anti-fraud arrangement which prevents an, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Telephone set having an anti-fraud arrangement which prevents an will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1455996