Patent US4885767A successfully refreshed from Google Patents.
US4885767A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Blue-box fraud prevention
Assignee: Bell Canada Inc
•
Filing: 1988-09-29
•
Granted: 1989-12-05
•
Expires: 2008-09-29
Abstract
Abstract Disclosed is a method and apparatus for detecting a fraudulent toll telephone call made by a device coupled to a telephone, which device can generate a single-frequency (SF) tone control signal and multi-frequency (MF) signals used in a toll telephone network. The method comprises the steps of, (a) identifying an off-hook condition on a toll analog SF trunk line by detecting loop current on the trunk, and (b) detecting on the trunk an SF tone control signal indicating an on hook condition, followed by a predetermined number of MF control signals. The fraudulent call can be cancelled by actuating a relay having contacts in at least one control lead of the SF trunk.
Inventors
- 👤 John L. Therrien
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 23:02
CPC Classifications
H; H04; H04M; H04M15/00; H04M15/10; H04M15/12; H04M15/24
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
89 words
A method of detecting a fraudulent toll telephone call made by means of a device coupled to a telephone, which device can generate a single-frequency (SF) tone control signal and multifrequency (MF) signals used in a toll telephone network, said method comprising the steps of: (a) identifying an off-hook condition on a toll analog SF trunk line by detecting loop current on said trunk, and (b) detecting on said trunk an SF tone control signal indicating an on hook condition, followed by a predetermined number of MF control signals.
Claim 2
Independent Claim
89 words
A method of detecting a fraudulent toll telephone call made by means of a device coupled to a telephone, which device can generate a single-frequency (SF) tone control signal and multifrequency (MF) signals used in a toll telephone network, said method comprising the steps of: (a) identifying an off-hook condition on a toll analog SF trunk line by detecting loop current on said trunk, and (b) detecting on said trunk an SF tone control signal indicating an on hook condition, followed by a predetermined number of MF control signals.
Claim 3
Dependent Claim
19 words
A method as claimed in claim 1 and further comprising the step of effecting cancellation of said fraudulent call.
Claim 4
Dependent Claim
13 words
A method as claimed in claim 2 wherein said predetermined number is three.
Claim 5
Dependent Claim
31 words
A method as claimed in claim 3 wherein cancellation of said fraudulent call is effected by actuating a relay having contacts in at least one control lead of said SF trunk.
Claim 6
Dependent Claim
130 words
Apparatus for detecting a fraudulent toll telephone call made by means of a device coupled to a telephone, which device can generate a single-frequency (SF) tone control signal and multi-frequency (MF) signals used in a toll telephone network, said apparatus comprising: (a) monitoring means for producing a first signal indicative of an off-hook condition on a toll analog SF trunk, (b) detection means activated in response to said first signal for detecting an SF tone control signal indicating an on hook condition and producing a second signal indicative thereof, (c) MF receiver means activated in response to said second signal for detecting MF control signals and, (d) switching means, responsive to receipt of a predetermined number of MF signals by said MF receiver, for effecting cancellation of said fraudulent call.
Claim 7
Dependent Claim
130 words
Apparatus for detecting a fraudulent toll telephone call made by means of a device coupled to a telephone, which device can generate a single-frequency (SF) tone control signal and multi-frequency (MF) signals used in a toll telephone network, said apparatus comprising: (a) monitoring means for producing a first signal indicative of an off-hook condition on a toll analog SF trunk, (b) detection means activated in response to said first signal for detecting an SF tone control signal indicating an on hook condition and producing a second signal indicative thereof, (c) MF receiver means activated in response to said second signal for detecting MF control signals and, (d) switching means, responsive to receipt of a predetermined number of MF signals by said MF receiver, for effecting cancellation of said fraudulent call.
Claim 8
Dependent Claim
12 words
Apparatus as claimed in claim 5 wherein said predetermined number is three.
Claim 9
Dependent Claim
25 words
Apparatus as claimed in claim 6 wherein said switching means comprises a relay having contacts in at least one control lead of said SF trunk.
Claim 10
Dependent Claim
15 words
Apparatus as claimed in claim 7 wherein said monitoring means is a loop current detector.
Claim 11
Dependent Claim
15 words
Apparatus as claimed in claim 7 wherein said MF receiver comprises an integrated circuit chip.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-12-04 | 1993-06-05 | 1993-12-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-12-04 | 1997-06-05 | 1997-12-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-12-04 | 2001-06-05 | 2001-12-05 | $7700.00 | Window Closed / Lapsed |