Patent FR586018A successfully refreshed from Google Patents.
Patent US3899640A successfully refreshed from Google Patents.
US3899640A
Expired / Lapsed
US
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Device for blocking toll calls from subscriber telephones
Assignee: Italtel SpA
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Filing: 1972-12-18
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Granted: 1975-08-12
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Expires: 1992-12-18
Abstract
Abstract To prevent the unauthorized initiation of toll calls from a subscriber station of a telephone system, the telephone set is equipped with monitoring circuitry working into a binary/decimal counter which is activated during the dialing of the first (or some other specified) digit and, in response to one or more predetermined values of that digit, trips a flip-flop to place a shunt across the line loop with concurrent generation of a busy signal. The flip-flop is also tripped if dialing is commenced before reception of a dial tone from the central office. Spurious dial pulses generated by manipulation of the hook switch, registered by the counter as a first digit but too short to actuate the switching equipment of the central office, are recognized by a detector in the monitoring circuitry and trip the same flip-flop.
Inventors
- 👤 Luigi Piacente
- 👤 Sanzio Capannini
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 17:49
CPC Classifications
H; H04; H04M; H04M1/00; H04M1/66; H04M1/677
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
232 words
A device for blocking the initiation of certain outgoing calls, characterized by a predetermined numerical value of a specified call-number digit, from a subscriber station of a telecommunication system connected via an outgoing line to a central office, comprising: monitoring circuitry at said station connected across said line for detecting dial pulses generated at said station by a call selector periodically opening and closing a line loop; pulse-shaping means in said circuitry for generating trains of stepping pulses in the rhythm of said dial pulses; integrating means connected to said pulse-shaping means for deriving an individual digital pulse from any train of stepping pulses; an electronic pulse counter connected to said circuitry for receiving said stepping pulses therefrom, said counter having at least one output lead electrically marked in response to a predetermined number of consecutive stepping pulses; control means connected to said integrating means and responsive to a predetermined digital pulse in a sequence of such digital pulses for passing a concurrently generated train of said stepping pulses to said counter; electronic switch means connected to said output lead for shunting said call selector, thereby preventing effective opencircuiting of said line loop and attenuating the dial pulses transmitted to said central office; and detector means connected to said pulse-shaping means for operating said switch means independently of said counter in response to spurious dial pulses of less than a predetermined duration.
Claim 2
Independent Claim
232 words
A device for blocking the initiation of certain outgoing calls, characterized by a predetermined numerical value of a specified call-number digit, from a subscriber station of a telecommunication system connected via an outgoing line to a central office, comprising: monitoring circuitry at said station connected across said line for detecting dial pulses generated at said station by a call selector periodically opening and closing a line loop; pulse-shaping means in said circuitry for generating trains of stepping pulses in the rhythm of said dial pulses; integrating means connected to said pulse-shaping means for deriving an individual digital pulse from any train of stepping pulses; an electronic pulse counter connected to said circuitry for receiving said stepping pulses therefrom, said counter having at least one output lead electrically marked in response to a predetermined number of consecutive stepping pulses; control means connected to said integrating means and responsive to a predetermined digital pulse in a sequence of such digital pulses for passing a concurrently generated train of said stepping pulses to said counter; electronic switch means connected to said output lead for shunting said call selector, thereby preventing effective opencircuiting of said line loop and attenuating the dial pulses transmitted to said central office; and detector means connected to said pulse-shaping means for operating said switch means independently of said counter in response to spurious dial pulses of less than a predetermined duration.
Claim 3
Dependent Claim
82 words
A device as defined in claim 1 wherein said detector means comprises a first pair of parallel branches, one of said branches including delay means for retarding an incoming dial pulse by said predetermined duration, the other of said branches including differentiation means for deriving a spike from the trailing edge of an incoming dial pulse, and coincidence means connected to said branches for generating an operating signal for said switch means upon occurrence of said spike before the retarded dial pulse.
Claim 4
Dependent Claim
88 words
A device as defined in claim 1 wherein said circuitry further includes a receiver for alternating-current signals from said central office, a discriminating circuit including storage means connected to said receiver and said pulse-shaping means for determining the presence of a dial tone from the central office prior to generation of the first stepping pulse, and a connection from said storage means to said switch means for operating the latter independently of said contour upon the occurrence of a stepping pulse in the absence of such dial tone.
Claim 5
Dependent Claim
55 words
A device as defined in claim 3, furthEr comprising sensing means responsive to current flow in said line loop and a trigger circuit connected to said storage means and said sensing means for operating said switch means independently of said counter upon prolonged interruption of the line loop following the occurence of a dial tone.
Claim 6
Dependent Claim
43 words
A device as defined in claim 4, further comprising a tone generator controlled by said switch means for placing a busy signal on said line concurrently with the shunting of said call selector, said trigger circuit including inhibiting means for said tone generator.
Claim 7
Dependent Claim
50 words
A device as defined in claim 1 wherein said switch means comprises a flip-flop, a switch controlled by said flip-flop and gate means between said flip-flop and said switch connected to said integrating means for preventing actuation of said switch by said flip-flop in the absence of a digital pulse.
Claim 8
Independent Claim
223 words
A device for blocking the initiation of certain outgoing calls, characterized by a predetermined numerical value of a specified call-number digit, from a subscriber station of a telecommunication system connected via an outgoing line to a central office, comprising: monitoring circuitry at said station connected across said line for detecting dial pulses generated at said station by a call selector periodically opening and closing a line loop; pulse-shaping means in said circuitry for generating trains of stepping pulses in the rhythm of said dial pulses; integrating means connected to said pulse-shaping means for deriving an individual digital pulse from any train of stepping pulses; an electronic pulse counter connected to said circuitry for receiving said stepping pulses therefrom, said counter having at least one output lead electrically marked in response to a predetermined number of consecutive stepping pulses; control means connected to said integrating means and responsive to a predetermined digital pulse in a sequence of such digital pulses for passing a concurrently generated train of stepping pulses to said counter; electronic switch means connected to said output lead for shunting said call selector, thereby preventing effective open-circuiting of said line loop and attenuating the dial pulses transmitted to said central office; and inhibiting means connected to said integrating means for making said switch means ineffectual in the absence of a digital pulse.
Claim 9
Independent Claim
223 words
A device for blocking the initiation of certain outgoing calls, characterized by a predetermined numerical value of a specified call-number digit, from a subscriber station of a telecommunication system connected via an outgoing line to a central office, comprising: monitoring circuitry at said station connected across said line for detecting dial pulses generated at said station by a call selector periodically opening and closing a line loop; pulse-shaping means in said circuitry for generating trains of stepping pulses in the rhythm of said dial pulses; integrating means connected to said pulse-shaping means for deriving an individual digital pulse from any train of stepping pulses; an electronic pulse counter connected to said circuitry for receiving said stepping pulses therefrom, said counter having at least one output lead electrically marked in response to a predetermined number of consecutive stepping pulses; control means connected to said integrating means and responsive to a predetermined digital pulse in a sequence of such digital pulses for passing a concurrently generated train of stepping pulses to said counter; electronic switch means connected to said output lead for shunting said call selector, thereby preventing effective open-circuiting of said line loop and attenuating the dial pulses transmitted to said central office; and inhibiting means connected to said integrating means for making said switch means ineffectual in the absence of a digital pulse.
Claim 10
Independent Claim
330 words
A device for blocking the initiation of certain outgoing calls, characterized by a predetermined numerical value of a specified call-number digit, from a subscriber station of a telecommunication system connected via an outgoing line to a central office, comprising: monitoring circuitry at said station connected across said line for detecting dial pulses generated at said station by a call selector periodically opening and closing a line loop; pulse-shaping means in said circuitry for generating trains of stepping pulses in the rhythm of said dial pulses; integrating means connected to said pulse-shaping means for deriving an individual digital pulse from any train of stepping pulses; an electronic pulse counter connected to said circuitry for receiving said stepping pulses therefrom, said counter having at least one output lead electrically marked in response to a predetermined number of consecutive stepping pulses; control means connected to said integrating means and responsive to a predetermined digital pulse in a sequence of such digital pulses for passing a concurrently generated train of said stepping pulses to said counter; electronic switch means connected to said output lead for shunting said call selector, thereby preventing effective open-circuiting of said line loop and attenuating the dial pulses transmitted to said central office; a receiver for alternating-current signals from said central office; a discriminating circuit including storage means connected to said receiver via a time-constant network and further connected to said pulse-shaping means for deTermining the presence of a dial tone from the central office prior to generation of the first stepping pulse, said storage means being connected to said switch means for operating the latter independently of said counter upon the occurrence of a stepping pulse in the absence of such dial tone; sensing means responsive to current flow in said line loop; and a trigger circuit connected to said storage means and said sensing means for operating said switch means independently of said counter upon prolonged interruption of the line loop following the occurrence of a dial tone.
Claim 11
Independent Claim
330 words
A device for blocking the initiation of certain outgoing calls, characterized by a predetermined numerical value of a specified call-number digit, from a subscriber station of a telecommunication system connected via an outgoing line to a central office, comprising: monitoring circuitry at said station connected across said line for detecting dial pulses generated at said station by a call selector periodically opening and closing a line loop; pulse-shaping means in said circuitry for generating trains of stepping pulses in the rhythm of said dial pulses; integrating means connected to said pulse-shaping means for deriving an individual digital pulse from any train of stepping pulses; an electronic pulse counter connected to said circuitry for receiving said stepping pulses therefrom, said counter having at least one output lead electrically marked in response to a predetermined number of consecutive stepping pulses; control means connected to said integrating means and responsive to a predetermined digital pulse in a sequence of such digital pulses for passing a concurrently generated train of said stepping pulses to said counter; electronic switch means connected to said output lead for shunting said call selector, thereby preventing effective open-circuiting of said line loop and attenuating the dial pulses transmitted to said central office; a receiver for alternating-current signals from said central office; a discriminating circuit including storage means connected to said receiver via a time-constant network and further connected to said pulse-shaping means for deTermining the presence of a dial tone from the central office prior to generation of the first stepping pulse, said storage means being connected to said switch means for operating the latter independently of said counter upon the occurrence of a stepping pulse in the absence of such dial tone; sensing means responsive to current flow in said line loop; and a trigger circuit connected to said storage means and said sensing means for operating said switch means independently of said counter upon prolonged interruption of the line loop following the occurrence of a dial tone.
Claim 12
Dependent Claim
33 words
A device as defined in claim 6, further comprising a tone generator controlled by said switch means for placing a busy signal on said line concurrently with the shunting of said call selector.
Claim 13
Dependent Claim
34 words
A device as defined in claim 9 wherein said trigger circuit includes blocking means for said tone generator effective upon operation of said switch means in response to prolonged interruption of the line loop.
References Cited (Backward Citations)
US3651275A
Cited
US3748396A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-08-11 | 1979-02-10 | 1979-08-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-08-11 | 1983-02-10 | 1983-08-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-08-11 | 1987-02-10 | 1987-08-12 | $7700.00 | Window Closed / Lapsed |