Telephonic communications – Telephone line or system combined with diverse electrical... – Having transmission of a digital message signal over a...
Reexamination Certificate
2001-01-19
2003-05-06
Chan, Wing (Department: 2643)
Telephonic communications
Telephone line or system combined with diverse electrical...
Having transmission of a digital message signal over a...
C379S090010, C379S399010
Reexamination Certificate
active
06560319
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of wired communication systems, and, more specifically, to the networking of devices over telephone wiring via outlet connections.
BACKGROUND OF THE INVENTION
There is an ongoing trend toward using telephone wiring within a building as media for data communication. As part of the Public Switched Telephone Network (PSTN), telephone wiring is both common and widespread, and is typically configured for the voice spectrum to enable speech communication from one telephone to another. It is well-known in the art that such a system can be used for data communication as well as telephony by employing frequency domain/division multiplexing (FDM) which splits the bandwidth carried by a wire into a low-frequency band capable of carrying an analog telephony signal and a high-frequency band capable of carrying data communication or other signals. Such a mechanism is disclosed, for example, in U.S. Pat. No. 4,785,448 to Reichert et al. Using telephone wiring for both telephony and additional service is disclosed in U.S. Pat. No. 5,929,896 to Goodman et al. Also is common are xDSL systems, primarily Asymmetric Digital Subscriber Loop (ADSL) systems. Recently, there has also been a trend for using telephone wiring for data networking simultaneously with telephony and ADSL signals. Such systems are described, for example, in WO 99/12330 to Foley, U.S. Pat. No. 6,069,899 to Foley, U.S. Pat. No. 5,896,443 to Dichter (hereinafter referred to as “Dichter”), and others.
FIG. 1
shows a graph
10
which shows the frequency spectrum for FDM. A POTS signal
11
occupies the 0 to 4 KHz bandwidth, while ADSL signals
12
usually span from 100 KHz to 1.5 MHz, and in-home data network signals
13
(and similar applications) occupy the 5-10 MHz band.
The term “analog telephony” herein denotes traditional analog low-frequency audio voice signals typically under 3 KHz, sometimes referred to as “POTS” (“plain old telephone service”), whereas the term “telephony” in general denotes any kind of telephone service, including digital service such as Integrated Services Digital Network (ISDN). The term “high-frequency” herein denotes any frequency substantially above such analog telephony audio frequencies, such as that used for data. ISDN typically uses frequencies not exceeding 100 KHz (typically the energy is concentrated around 40 KHz). The term “telephone line” herein denotes electrically-conducting lines which are intended primarily for the carrying and distribution of analog telephony, and includes, but is not limited to, such lines which may be pre-existing within a building and which may currently provide analog telephony service. The term “telephone device” herein denotes, without limitation, any apparatus for telephony (including both analog telephony and ISDN), as well as any device using telephony signals, such as fax, voice-modem, and so forth. The term “Data Terminal Equipment” (DTE) herein refers to any device or apparatus which can handle or process data, including, but not limited to, computers and controllers. The term “data communications” herein refers to the sending and/or receiving of data between any devices or apparatus, including, but not limited to, network communications such as a local area network.
FIG. 2
schematically illustrates a prior-art in-home telephone wiring system
20
. A junction box (not shown) is used to separate the in-home circuitry from the PSTN and is used as a test facility for troubleshooting as well as for wiring new telephone outlets in the home. A telephone set
26
a
connects to the telephone wiring, which is usually a wire pair
21
a
and
21
b
. Connection is done via a telephone outlet
22
, of which there are commonly a number located at convenient places within the home, and which typically utilize a standard RJ-11 (“Registered Jack”) connector, which employs either four or six contacts (pins).
FIG. 2
illustrates the six-pin RJ-11 form, although the four-pin configuration is also common in North America. Telephone outlet
22
has a female RJ-11 connector
23
(usually referred to as the “jack”). Telephone set
26
a
may be connected to outlet
22
via a male RJ-11 connector
24
(often referred to as a “plug”). In most cases, the center pins
3
and
4
are used for making the connection. In the four-pin configuration (not shown), the center pins are numbered
2
and
3
. The terms “standard connector”, “standard telephone connector”, and “standard data connector” are used in the description and appended claims to denote any connectors which are industry-standard or de facto standard connectors.
As suggested by the current trends, there is a widespread demand to use existing telephone wiring for both telephony and data networking. In this way, the task of establishing a new local area network in a home or other building is eased, because there are no additional wires to install. As previously noted, frequency domain/division multiplexing provides a means of simultaneously carrying an analog telephony signal and data communication or other signals.
In order to allow for both telephony and data networking without any mutual interference, a set of filters is commonly used. A Low Pass Filter (LPF) is connected in series with the telephone for passing the telephony signal (0-4 KHz band) and isolating the high frequency band. Similarly, a High Pass Filter (HPF) is connected in series with the modem used for the data communication. The term “low pass filter” herein denotes any device that passes signals in the low-frequency (analog telephony) band but blocks signals in the high-frequency (data) band. Conversely, the term “high pass filter” herein denotes any device that passes signals in the high-frequency (data) band but blocks signals in the low-frequency (analog telephony) band. The term “data device” herein denotes any apparatus that handles digital data, including without limitation modems, transceivers, Data Communication Equipment, and Data Terminal Equipment.
FIG. 3
illustrates part of a prior-art network
30
. Low pass filters
31
a
and
31
b
are connected to telephone sets
26
a
and
26
b
respectively. DTE's
34
a
and
34
b
intercommunicate via modems
33
a
and
33
b
, respectively, which are connected to telephone line pair
21
a
and
21
b
via high pass filters
32
a
and
32
b
, respectively. Low pass filters such as
31
a
and
31
b
are also referred to as “micro-filters”.
FIG. 4
shows an example of a prior-art low pass filter
31
. Inductors
41
a
and
41
b
are placed in series with the connections to pins
3
and
4
, respectively, while capacitors
42
a
and
42
b
are connected in parallel between pins
3
and
4
. LPF
31
a
is connected in series with telephone set
26
a
, as shown in FIG.
4
. Capacitors
42
a
and
42
b
reduce noise produced by telephone
26
a
in the high-frequency data communication band, and also reduce degradation resulting from the addition of taps in the telephone connection, which are often not terminated properly.
High pass filters
32
a
and
32
b
(
FIG. 3
) are usually included within modems
33
a
and
32
b
. Furthermore, both modems
33
a
and
32
b
and high pass filters
32
a
and
32
b
are usually housed within DTE's
34
a
and
34
b
. A typical example of DTE
34
a
is a personal computer with modem
33
a
and high pass filter
32
a
within a plug-in card (known as a “Network Interface Card”—“NIC”), installed in the computer housing. However, since it is not practical to change or modify telephones or telephone wiring, the low pass filter
31
must be an add-on module.
One common prior-art implementation of the low pass filter
31
is as a module having an RJ-11 plug and jack, for being connected externally between telephone set
26
a
and jack
23
within outlet
22
(FIG.
2
). To an ordinary non-technically skilled user, however, the requirement for such a module might present difficulties. A casual user, such as a person in an office or a family member wishing to attach a telephone to an outlet, might not be awa
Browdy and Neimark , P.L.L.C.
Chan Wing
Serconet Ltd.
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