Telephonic communications – Telephone line or system combined with diverse electrical... – Having transmission of a digital message signal over a...
Reexamination Certificate
1999-08-20
2001-10-09
Woo, Stella (Department: 2643)
Telephonic communications
Telephone line or system combined with diverse electrical...
Having transmission of a digital message signal over a...
C379S093090, C379S027010
Reexamination Certificate
active
06301340
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates in general to telephone systems and networks, and is particularly directed to a new and improved mechanism that is connectable with and may be integrated within transceiver card and network termination interface components of an integrated services digital network telephone system, for providing auxiliary, substitute telephone service capability (plain old telephone service or POTS) between an auxiliary analog telephone installed at a customer premises site and an integrated services digital network communication path (either extended or non-extended) to a line card of a central office switch, in the event of a power outage at the customer premises.
BACKGROUND OF THE INVENTION
Integrated services digital network (ISDN) communication systems enable telephone service providers to supply multiple types of signalling channels from a central office over a signal local loop twisted pair to a network termination interface at a customer premises site.
FIG. 1
diagrammatically illustrates a reduced complexity example of a typical extended distance ISDN communication system, while
FIG. 2
diagrammatically illustrates a non-extended distance ISDN communication system. The extended distance ISDN system of
FIG. 1
is intended to enable a telephone service provider to supply multiple types of signalling channels from a central office (CO) site
10
over a PCM link (such as an optical fiber link) to a remotely located customer premises equipment (CPE) site
20
, while the non-extended network of
FIG. 2
provides a local loop directly from the central office to the customer premises site. ISDN signalling channels typically include digital data channels and/or digitized voice channels, as well as a separate administrative channel that conveys call control information.
More particularly, in the extended distance system of
FIG. 1
, the central office site
10
, which is located at a ‘west’ end of an extended (PCM) communication link
30
, includes a central office switch
11
(such as a 5ESS switch manufactured by AT&T), which contains a plurality of line termination circuits (or line cards), one of which is shown at
12
. For extended distance communications carried out by the system of
FIG. 1
, line card
12
is coupled over a local loop (twisted tip/ring pair)
13
to what is termed in the telephone industry as a U Basic Rate-One Transmission Extension (U-BR1TE) transceiver card
14
(also known in the industry as a Basic Rate Interface Transmission Extension (U-BRITE) card).
The U-BR1TE (or U-BRITE) card contains an ISDN transceiver unit and an associated PCM bus interface which are operative to transmit and receive standard 2B+D ISDN data traffic over a PCM digital data link, such as a T
1
=1.544 MB/s link, and to interface the ISDN signals via the local loop to and from loop termination equipment. Namely, the U-BR1TE card
14
interfaces the local loop
13
with a digital data link
30
for PCM communications transport to another U-BR1TE transceiver card
24
at the east end of the link
30
, serving the customer premises equipment (CPE) site
20
. The U-BR1TE transceiver card
24
is, in turn, coupled over a local loop (twisted tip/ring pair)
23
to a network termination interface (NT-1) circuit
21
, to which customer premises equipment, such as an ISDN data terminal, shown at
22
, is coupled. In the non-extended system configuration of
FIG. 2
, the local loop
13
from a respective line card
12
in the central office switch
11
, rather than being coupled to a U-BR1TE transceiver card, is coupled directly to the network termination interface (NT-1) circuit
21
.
In either system configuration, since the network termination interface
21
is customer-installed (and therefore locally powered at the customer premises site
20
, rather than being powered by the central office
10
, as in the case of a conventional POTS telephone), the local telephone service provider is unable to interfere with the customer's choice of equipment to be connected to the ISDN line, such as the installation of equipment that provides a battery back-up in the event of a power outage.
Although the public service commissions of local jurisdictions where customer premises equipment is installed require that telephone service providers (regional Bell operating companies) ensure that each customer be provided with emergency (911) telephone service, the service provider is currently not permitted to dictate that the customer install a particular piece of equipment, such as one that will provide back-up battery for the network termination interface during a power outage. As a consequence, service providers customarily require their residential customers to maintain a separate POTS line as an emergency adjunct to the ISDN service, so that the residential customer is, in effect, forced to subscribe to an additional form of ‘fire insurance’. Namely, the extra POTS line is intended to prevent residential customers from losing access to telephone service, particularly in the event of an emergency, where expedient 911 service may be critical. Such a requirement obviously constitutes a substantial cost penalty to the customer, who is faced with both a potential installation fee, and an unwanted monthly bill for a normally unused POTS line.
SUMMARY OF THE INVENTION
In accordance with the present invention, the need to ensure continuous telephone service to a residential customer premises served by an ISDN line, without requiring that the customer maintain an additional POTS line as an emergency back-up to the normally used ISDN service, is successfully addressed by a modification of conventional ISDN signalling circuits and network termination interface components, together with an augmentation of the communication control software employed therein, so that, in the event of a loss of power to customer premises equipment, a communication link between an auxiliary POTS telephone and an ISDN communication path to the central office may be established.
In accordance with a first embodiment of the invention, the U-BR1TE card of an extended distance ISDN system, and network termination interface at the customer premises site are respectively replaced with a modified U-BR1TE card and a modified network termination interface, which selectively provide auxiliary communication capability over the extended ISDN line with an auxiliary POTS telephone, that is connectable to the modified network termination interface. Advantageously, in this and other embodiments of the invention, there is no modification of the central office switch, per se, so that the integrity of the ISDN communication path with the central office line card remains unaffected. As a result, the central office equipment can continue to conduct standard ISDN communications with the customer premises equipment, even though the customer is employing a POTS back-up phone.
Pursuant to the first embodiment of the invention, the architecture of the U-BR1TE card is modified to include an auxiliary digital/analog interface, an auxiliary loop relay, and a loss of power monitoring mechanism which is associated with the card's microcontroller. In the event of an emergency POTS mode of operation, the microcontroller operates the loop relay and thereby substitutes the auxiliary digital/analog interface in place of normally employed ISDN transceiver circuitry. Respective transmit and receive links of a PCM bus are terminated by way of a standard PCM bus interface unit which is controlled by the microcontroller and is also coupled to an ISDN U-transceiver interface. The ISDN U-transceiver interface customarily directly ports industry standard 2B1Q-formatted symbols with respective tip and ring leads of a local twisted cable pair loop that services the customer premises equipment.
The auxiliary digital/analog interface contains a codec unit and a subscriber loop interface (SLI), which are controllably connected in circuit between the local loop and the PCM bus interface in dependence upon the state of op
Sansom Michael Scott
Schneider Kevin W.
Adtran Inc.
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Woo Stella
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