Circuit to provide backup telephone service for a multiple service access system using a twisted pair

• US 6,347,075 B1
• Filed: 12/31/1997
• Issued: 02/12/2002
• Est. Priority Date: 12/31/1997
• Status: Expired due to Term

• Current Assignee: AT&T Corporation (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Barzegar, Farhad, Gerszberg, Irwin, Treventi, Philip Andrew
• Primary Examiner(s): Nguyen, Chau
• Assistant Examiner(s): Nguyen, Phuongchau Ba
• Application Number:
  US09/001,343
• Time in Patent Office: 1,504 Days
• Field of Search: 370/216, 370/225, 370/228, 370/494, 379/93.08
• US Class Current: 370/228
• CPC Class Codes: H04M 3/005 Interface circuits for subscriber lines current supply H04M19/00 and subgroups; supervisory, monitoring or testing arrangements H04M3/22 and subgroups; in key telephone systems H04M9/006
• CPC Class Codes: H04M 3/12 Marking faulty circuits "busy"; Enabling equipment to disengage itself from faulty circuits ; Using redundant circuits; Response of a circuit, apparatus or system to an error
• CPC Class Codes: H04M 3/2209 for lines also used for data transmission
• CPC Class Codes: H04M 3/30 for subscriber's lines , for the local loop

Abstract

A subscriber link to a central office which employs data compression, forward error correction, and advanced modulation techniques and to connect subscribers to multiple communications networks to provide an array of services. A device provides normal telephone service in the event of an equipment failure. At the subscriber end, a server called an intelligent services director (ISD) provides multiple independent connections for telephones which ordinarily connect to multiple access virtual circuits generated on the subscriber link over a twisted pair. A device called a facilities management platform (FMP) at the central office end of the link, among other things, provides interfacing of the subscriber link to various networks including a digital subscriber loop (DLC) and packet switched networks. Ordinarily telephones connected to the ISD require power and correctly functioning modems and controllers in the ISD and the FMP to have access to the outside world. A fail-safe mechanism, however allows at least one chosen phone to function in the event of a failure. The chosen phone must be capable of pulse or DTMF dialing. The connection through which it operate can be switched directly to the twisted pair media connecting to the FMP. At the FMP, the twisted pair is switched to tie the connection directly to a line card of the DLC. Alternatively, the ISD contains an interface to a specialized phone designed for the ISD environment. The interface provides the appearance to the DLC of a regular POT.

Claims

1. A fail safe mechanism for a subscriber link over a conductor connecting a subscriber server with at least one telephone device to a telephone network facility, comprising:

a fail safe connection in said subscriber server for said at least one telephone device, said fail safe connection being switchable between a normal position connecting said at least one telephone device to said subscriber server and a backup position connecting directly to said conductor;

said telephone network facility having a telephone network termination configured to connect an analog telephone;

a network interface terminating a link layer of said subscriber link at said telephone network facility;

a switch on said network interface such that said conductor is switchable between said network interface and said termination, whereby said at least one telephone device is connectable to said telephone network termination when said fail safe connection is in said backup position; and

an analog interface in one of said subscriber server and said at least one telephone device connected to permit said at least one telephone to function as an analog telephone.

2. A mechanism as in claim 1, wherein said telephone network termination provides battery-backup power for said analog telephone.

3. A safety device for multiple access subscriber link over a wire pair connecting a subscriber server to at least first and second network interfaces, said first network interface having a port directly connectable by a conductor to a phone such that said phone is operable without power being supplied to said phone, said device comprising:

a remote modem at said second network interface connected to said subscriber link;

said local modem of said server in communication with said remote modem over said subscriber link;

a telephone using a first range of frequencies in a frequency spectrum of said subscriber link;

said local modem and said remote modem using a second range of frequencies in said frequency spectrum;

said telephone being connected directly to said remote modem through said wire pair at a remote end of said wire pair, said remote end of said wire pair connected to said port directly and selectably through a switch; and

said switch is controlled by a controller and said controller closes said switch responsively to an occurrence of a failure of one of said remote and said local modems.

4. A safety device for multiple access subscriber link over a wire pair connecting a subscriber server to at least first and second network interfaces, said first network interface having a port directly connectable by a conductor to a phone such that said phone is operable without power being supplied to said phone, said device comprising:

a remote modem at said second network interface connected to said subscriber link;

said local modem of said server in communication with said remote modem over said subscriber link;

a telephone using a first range of frequencies in a frequency spectrum of said subscriber link;

said local modem and said remote modem using a second range of frequencies in said frequency spectrum;

said telephone being connected directly to said remote modem through said wire pair at a remote end of said wire pair, said remote end of said wire pair connected to said port directly and selectably through a switch; and

said switch is controlled by a controller and said controller closes said switch responsively to a failure to receive at said local modem a message from said remote modem or a failure to receive at said remote modem a message from said local modem.