Telephonic communications – Subscriber line or transmission line interface – Power supply
Reexamination Certificate
1998-02-24
2001-03-20
Hudspeth, David R. (Department: 2741)
Telephonic communications
Subscriber line or transmission line interface
Power supply
C379S093130, C379S093360
Reexamination Certificate
active
06205219
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a receiver for information transmitted on a telephone line. More particularly, it relates to the reception of call related information, e.g., Caller ID information, on a line side using an audio codec.
2. Background of Related Art
The reception of call related information before answering an incoming call is known. For instance, one call related information service is called Calling Identity Delivery (Caller ID), which is a well known and popular service provided by many telephone companies. This service provides the telephone number and household name information of a calling party to the called party before the call is answered. Based on a display of the Caller ID information, the called party may decide not to answer the incoming call. Basic Caller ID information is transmitted from the local telephone company to the called party while the called party's phone is in a hung-up or on-hook state, between the first and second rings. Customer premises equipment capable of receiving Caller ID (CID) information including Calling Number Delivery (CND) and Calling Name Delivery (CNAM) when the customer premises equipment is on-hook is generally referred to as Type
1
customer premises equipment.
Waveform (a) of
FIG. 6
depicts the signal on a telephone line including Caller ID information transmitted from a central office to customer premises equipment. As depicted, the Caller ID information is transmitted to the customer premises equipment as marks and spaces between a first and second ring signal. Waveform (b) of
FIG. 6
shows the approximate current draw allowed by customer premises equipment from a telephone line while the customer premises equipment is on-hook or hung-up, according to current standards in the United States. Although the customer premises equipment is permitted to draw additional power from the telephone line approximately during and between the first and second ring signals while the customer premises equipment is on-hook, even this additional power is extremely limited both in amplitude and in duration. Moreover, although customer premises equipment is permitted to draw significantly more power while in an off-hook condition, Type
1
Caller ID information is received entirely while the customer premises equipment is on-hook. Because of the limited amount of current available from the telephone line while the customer premises equipment is in an on-hook state, most devices which receive Caller ID information are either powered by an external power source, or are generally non-linear analog circuits.
Conventional circuits exist for receiving call related information on a line side of a telephone circuit. For instance,
FIG. 7
shows a conventional analog circuit for receiving call related information, e.g., Caller ID.
In
FIG. 7
, call related information is coupled through capacitors
702
,
704
and transformer T
1
even when the on-hook switch
706
is open. Ring signals are detected by opto-isolator OPTO
1
. The circuit of
FIG. 7
is entirely analog. Isolation between the high voltage, line side of the circuit (the right side in
FIG. 7
) and the low voltage side of the circuit (the left side in
FIG. 7
) is provided by transformer T
1
.
FIG. 8
shows another conventional circuit for receiving call related information. In
FIG. 8
, the circuit for receiving the call related information, e.g., Caller ID, is an analog circuit separated from the main signal path of the telephone circuit. The call related information signal path is isolated by isolation capacitors
808
,
810
, and differentially input to an operational amplifier (op amp)
820
via resistors
804
,
806
. The output of the op amp
820
is input to a codec
830
, which digitizes the signal for processing by the digital signal processor (DSP)
840
.
In
FIG. 8
the call related information circuit is an analog circuit with the codec
830
being on the low voltage side of isolation capacitors
808
,
810
. The codec
830
is powered by an external source in the conventional circuit of FIG.
8
. Moreover, ring signals may be detected either by the opto-isolator
708
or through the call related information signal path.
Call related information receiving circuits such as those shown in
FIGS. 7 and 8
require extra circuits or require that an audio codec, e.g.,
730
(
FIG. 7
) and
830
(FIG.
8
), be in a powered-on condition which is wasteful. For example, a call related information device may be battery or line powered, relocated easily from place to place, and installed in any convenient telephone jack. For convenience purposes it may be desirable to not provide the call related information device with an external power source. Thus, in these type situations, extra circuits or audio codecs may be wasteful of available battery or line power.
Similarly,
FIG. 9
shows yet another conventional circuit for receiving call related information that requires extra circuits. In
FIG. 9
, the circuit for receiving call related information is a digital circuit separated from the main signal path of the telephone circuit.
In particular, as shown in
FIG. 9
, a tip signal T and a ring signal R from a telephone line are input to a filter
918
and an analog amplifier
916
, which amplifies the analog signal including the call related information from the telephone line. The output of the analog amplifier
916
is input to a limit/slice circuit
914
, which forms a digital signal for processing by the OOK modulator
912
. The OOK modulator
912
provides on-off keying at the FSK rate to pass the call related information to the DSP
940
through isolation capacitors
902
,
904
. The DSP
940
includes an FSK decode module to decode the call related information and output the call related information, e.g., Caller ID data including CND and CNAM, for storage in log memory and/or for display.
In
FIG. 9
, the codec
930
remains on the low voltage side of the telephone circuit, i.e., isolated from the telephone line, in this case by isolation capacitors
902
,
904
and transformer T
1
. The codec
930
is powered by an external source, and is not in the path of reception of call related information. Ring signals may be detected either by the opto-isolator
708
or through the call related information signal path, but in either case amplitude information with respect to the ring signal is not detected.
There is a need for low power elements allowing processing in a digital call related information signal path on a high voltage side of a telephone circuit.
SUMMARY OF THE INVENTION
In accordance with the principles of the present invention, a line-powered device receives data from a telephone line in an on-hook state. The device includes a line-powered 1
st
order or other very low power codec sigma-delta analog-to-digital converter which digitizes an analog signal from the telephone line to digital samples. A digital filter filters the digital samples output from the first order sigma-delta analog-to-digital converter, and a line-powered frequency shift keying decoder decodes a filtered signal from the filtered digital signal, and outputs decoded data.
A method is also disclosed for receiving data from a telephone line in an on-hook state. An analog signal from a telephone line is digitized using a line-powered 1
st
order sigma-delta analog-to-digital converter. The data is digitally decoded from an output of the 1
st
order sigma-delta analog-to-digital converter, and decoded data is provided.
REFERENCES:
patent: 4851841 (1989-07-01), Sooch
patent: 4852152 (1989-07-01), Honick
patent: 5086454 (1992-02-01), Hirzel
patent: 5189419 (1993-02-01), Lyden
patent: 5369687 (1994-11-01), Farkas
patent: 5875235 (1999-02-01), Mohajeri
patent: 5940019 (1999-08-01), Maejima
Boser et al.; Quantization Error Spectrum of Sigma-delta Modulators; ISCAS 1988, pp. 2331-2334, 1988.*
Comino et al.; A First-Order Current-Steering Sigma-Delta Modulator; IEEE 1991; pp. 176-183, 1991.*
Yu et al.; Adaptive quantisation for one-bit sigma-delta modul
Hollenbach Keith Eugene
Laturell Donald Raymond
Witmer Steven Brooke
Azad Abul K.
Bollman William H.
Hudspeth David R.
Lucent Technologies - Inc.
LandOfFree
Call related information reception using sigma/delta modulation does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Call related information reception using sigma/delta modulation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Call related information reception using sigma/delta modulation will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2445770