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 Title: |
US4546213:
Modem security device
[ Derwent Title ]
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| Country: |
US United States of America
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| Inventor: |
Dick, William J.; Woodbury, NY 11797
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| Assignee: |
None
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| Published / Filed: |
1985-10-08
/ 1984-04-25
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| Application Number: |
US1984000603567
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| IPC Code: |
Advanced:
H04L 12/06;
H04L 12/22;
H04L 29/06;
H04M 11/06;
Core:
more...
IPC-7:
H04M 11/00;
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| ECLA Code: |
H04L29/06S14D; H04L12/06; H04L12/22; H04M11/06;
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| U.S. Class: |
Current:
379/093.02;
Original:
179/002.A;
179/002.C;
179/002.DP;
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| Field of Search: |
179/2 A,2 AM,2 C,2 CA,2 DP,84 C,84 VF
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| Priority Number: |
| 1984-04-25 |
US1984000603567 |
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| Abstract: |
A modem security access circuit device, which is coupled between a dial-up telephone line and an automatic-answering modem, includes a line matching transformer circuit which trips an incoming ringing signal for a predetermined time interval. During the predetermined interval the caller, who receives no indication of the presence of the modem, must send an access code consisting of a preselected sequence of up to ten digits from a DTMF tone pad, or else the line matching transformer circuit disconnects from the telephone line. The device also includes a decoding circuit coupled to the line matching transformer circuit for receiving the access code. If the correct access code is received, the decoding circuit activates a ring supply generator which provides an internal ring signal to activate the modem. The activated modem is then coupled to the telephone line through the line matching transformer circuit and a carrier signal is sent to the caller. In addition, the device includes a lock-out circuit which disables the decoding circuit for a preselected time interval if the caller sends a predetermined number of invalid digits. Furthermore, the device includes a counter circuit for counting the number of invalid digits received and an LED display for visual read-out of the invalid digit count.
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| Attorney, Agent or Firm: |
Brumbaugh, Graves, Donohue & Raymond ;
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| Primary / Asst. Examiners: |
Rubinson, Gene Z.; Brady, W. J.
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| Maintenance Status: |
E1 Expired Check current status
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| INPADOC Legal Status: |
Show legal status actions
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| Family: |
None
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First Claim:
Show all 11 claims |
I claim:
1. A circuit device for preventing unauthorized communication with an automatic-answering modem comprising:
- connection means for coupling to a telephone line including first means responsive to a line ringing signal on the telephone line for terminating the line with an appropriate impedance for a predetermined time interval;
- terminal means for coupling to the modem;
- decoding means responsive to a preselected sequence of dial signals on the telephone line during the predetermined interval for actuation thereof;
- second means responsive to the actuation of the decoding means for activating the modem and for coupling the terminal means to the connection means, and wherein the connection means includes third means responsive to the activation of the modem for maintaining the coupling between the terminal means and the connection means and for maintaining the termination of the telephone line by the first means thereby to establish communication between the modem and the telephone line.
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| Background / Summary: |
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| Drawing Descriptions: |
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| Description: |
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| Forward References: |
Show 19 U.S. patent(s) that reference this one
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