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Description  |
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FIELD OF THE INVENTION
This invention relates to apparatus for receiving and transmitting voice
messages and electronic representations of text or images, or both, over a
single communications line. In particular, the present invention provides
a universal port--a single channel voice and data communications
integrated circuit board that can be readily installed in conventional
telephone answering systems.
BACKGROUND OF THE INVENTION
Contemporary business has embraced two technologies that allow an
individual employee to be more efficient and productive. The first of
these technologies is voice messaging technology. In conventional voice
messaging technology, a caller first calls an intended recipient by
telephone. If the recipient of the call is absent, the caller is
automatically connected to the recipient's voice messaging system. This
system enables the caller to record a message for the recipient-subscriber
in the caller's own voice, which message is then stored in an electronic
format by the system. When subscriber calls into the system, he can play
back the voice message on his telephone by issuing suitable commands.
The second technology effecting modern business practices is the facsimile
machine or telecopier, which enables a sender to transmit a text or visual
image (collectively "data") via electronic medium to a remote location,
where the text or image may be printed out. Conventional facsimile
technology requires telecopy equipment at both the sending and receiving
stations, the first to encode the transmittal into electronic format and
the latter to decode the transmittal back to a text or visual image
suitable for printing.
Voice messaging and telecopy technologies have freed the employee from his
office, and have enabled the businessman to conduct a large part of his
work away from his home office. By calling in to his office from a remote
location, the executive can listen to voice messages. Likewise, the
facsimile machine has enabled the businessman to receive text or visual
images virtually anywhere in the world accessible by public telephone
lines.
An evolution of facsimile technology is the ongoing development of methods
and apparatus for receiving and storing in electronic format the
electronic representation of a facsimile transmittal. Such systems, known
generically as "Fax Mail" systems, permit an incoming telecopy transmittal
to be stored on a data storage system in electronic form, for later recall
by the system subscriber. In this manner, the intended recipient may, for
example, call into the office from a remote location, determine that a
facsimile transmittal is available for him, and then direct that the text
or image stored on the system be transmitted for printout to a facsimile
machine at the remote location.
Previously known telephone answering systems have employed different
integrated circuit components for receiving and transmitting voice
information and text or image information. For example, in the Aspen(TM)
telephone answering system sold by Octel Communications Corporation,
Milpitas, Calif., voice signals received by the system are processed
through an Analog Line Card ("ALC") which discretizes the signal into a
digital electronic format using conventional voice processing techniques.
Such analog processing circuitry is not suitable, however, for processing
digital data, or for interpreting dual-tone modulated frequency (DTMF)
signals (typically referred to as "Touchtones").
Voice system manufacturers have heretofore provided separate integrated
circuit modules to enable their voice processing systems to receive or
transmit text or image data. For example, Octel Communications Corporation
provides the 500D Data Module, to enable their voice mail systems to
receive and transmit facsimile messages. The 500D Data Module requires a
dedicated communications port separate from those channels used for
recording and transmitting voice messages, because a different protocol is
used in processing data rather than voice signals.
A drawback common to previously known telephone answering systems with the
ability to receive either voice signals or data was the inability to
permit the caller, on a continuing basis, to vary the type of incoming
signal. For example, in systems such as the 500D Data Module, once the
incoming call was determined to be either voice or data, it was directed
to the voice or data port of the telephone answering system for the
duration of the transmittal. Thus, these systems had no ability to
instantaneously monitor the incoming signal and to switch between voice
and data processing as required for a particular incoming signal.
It would therefore be desirable to provide an integrated circuit board for
receiving and transmitting voice signals and data over a single
communications line, and which has the ability to discriminate and switch
between voice and data processing modes as required to properly receive
the incoming signal.
It would further be desirable to provide an integrated circuit board having
single port voice and data capability in the form of a digital line card,
so that the card could be readily interchanged to upgrade a conventional
analog line card.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to
provide a universal port comprising an integrated circuit board for
receiving and transmitting voice signals and data over a single
communications line, and which has the ability to discriminate and switch
between voice and data processing modes as required to properly process
the incoming signal.
It is another object of this invention to provide an integrated circuit
board having single port voice and data capability in the form of a
digital line card, so that the card could be readily interchanged for an
analog line card to upgrade conventional electronic messaging systems.
These and other objects are accomplished in accordance with the principles
of the present invention by providing an integrated circuit board for
receiving and transmitting voice signals and data over a single
communications line. This digital line card has the ability to monitor an
incoming signal, to discriminate between voice, data and command signals,
for example, DTMF signals. The digital line card changes processing modes
as required in response to command signals received from the caller to
properly process the incoming signal.
The apparatus of the present invention comprises an integrated circuit
board or card intended to replace a conventional analog line card in a
conventional electronic messaging system. The electronic messaging system
interfaces with a telephone system and is capable of storing both voice
messages and data transmittals, for example, facsimile transmittals, in
electronic format. The digital line card comprises a central processing
unit, a digital signal processing integrated circuit, a controller and
dual-port random access memory.
The digital line card of the present invention is programmed using a
conventional programming language (C-assembler programming language) so
that the digital line card has the ability to discriminate between voice
signals, data signals (modulated frequency or MF) and command signals, for
example, DTMF. The digital line card includes programming that enables it
to continuously monitor the incoming signal, to detect commands inserted
within the data stream, and to switch between data and voice signal
processing on a real-time basis responsive to those command signals.
The digital line card also fulfills the functions of a conventional analog
line card by extracting desired information from the incoming signal,
digitizing that information, and making the processed signal available for
storage elsewhere in the electronic storage system. A digital line card
constructed in accordance with the present invention is intended for
insertion in a conventional voice processing system with no other required
hardware changes.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects and advantages of the invention will be
apparent upon consideration of the following detailed description, taken
in conjunction with the accompanying drawings, in which like reference
numerals refer to like parts throughout, and in which:
FIG. 1 is a block diagram of a voice messaging/data storage system with
which the present invention is intended for use; and
FIG. 2 is a block diagram of a digital line card constructed in accordance
with the present invention;
FIG. 3 is a block diagram of a digital signal processing cell shown in FIG.
2; and
FIG. 4 is a state diagram showing the operational states of a digital line
card constructed in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, a voice messaging/data storage system employing a
digital line card constructed in accordance with the present invention is
shown. Voice messaging/data storage system is connected to a central
office telephone switch and is capable of intercepting calls when the call
recipient is absent. The system comprises an electronic storage system
capable of interfacing with a public switch telephone network or a private
branch exchange/central office system, and includes an electronic storage
medium capable of storing both voice messages and facsimile transmittable
in electronic format.
When there is no answer for an incoming call, the system acquires control
of the call and interacts with the caller, providing pre-programmed
prompts as required to obtain information from, and provide information
to, the caller. These prompts concern, for example, whether the caller
desires to leave a voice message, a facsimile transmittal, or a composite
voice/data message. The voice message or data sent by the caller is stored
in electronic format for subsequent playback or print out, or both, by the
call recipient.
As shown in FIG. 1, voice messaging/data storage system 10 comprises
central processing unit (CPU) board 11, digital line card (DLC) 12, trunk
interface card (TIC) 13, system file card 14 and data storage device 15.
Components 11 through 15 are interconnected via communications bus 16.
Central processing unit 11, which may be, for example, a 80386
microprocessor, available from Intel Corporation, Santa Clara, Calif.,
controls the data transfer over bus 16 between digital line card 12, and
system file card 14.
Trunk interface card 13 couples digital line card 12 to the subscriber's
telephone switch 17. Trunk interface cards 13 contain the compression and
decompression and analog interface circuitry required for a particular
interface. Incoming calls are passed via TIC card 13 to digital line card
12, which processes the incoming signal and makes it available on bus 16.
TIC card 13 is connected only to its corresponding group of digital line
cards, not to bus 16.
System file card 14 is coupled to data storage device 15, for example a
conventional disk drive. Data storage device 15 stores the system files,
subscriber profiles, voice greetings and preprogrammed prompts, and
incoming voice messages, facsimile transmittals and composite voice/data
messages received by the system in electronic format.
In accordance with the present invention, digital line card 12 includes a
digital signal processing (DSP) semiconductor chip, for example, a
TMS320C31, available from Texas Instruments, Houston, Tex., that functions
as a single channel port for both voice and data communications. The DSP
chip may be programmed using, for example, C-assembler programming
language, so that the chip has the ability to discriminate between
incoming voice signals and data transmissions, as well as the capability
to detect command signals. This capability enables system 10 to switch
between facsimile reception modes and interactive, voice activated modes
upon receipt of the appropriate command signals.
Other than the digital line card described hereinafter, the components of
the apparatus of FIG. 1 are commercially available, and may comprise, for
example, the Aspen(TM) Voice Messaging System, sold by Octel
Communications Corporation, Milpitas, Calif. Using conventional
programming techniques, one skilled in the art may program the system in
accordance with the process diagrams disclosed in copending and commonly
assigned U.S. patent application Serial No. 08/033,618, filed Mar. 19,
1993, to provide, for example, a voice annotation capability for a
facsimile transmittal, as described therein.
Referring now to FIG. 2, digital line card ("DLC") 12 of the present
invention is shown in block diagram form as comprising six digital signal
processing cells (DSP cells) 20, an Intel 80386-SX central processor 21,
an Intel 82370 integrated peripheral controller 22, dynamic random access
memory ("DRAM") 23, boot memory 24 and additional control logic PCM ASIC
25 and SBI ASIC 26, described hereinafter. Each DLC supports 12 channels,
two channels per DSP cell.
Each DLC 12 has a controller section comprising an Intel 80386-SX
microprocessor and an 82370 integrated peripheral controller, both
available from Intel Corporation, Santa Clara, Calif. The 80386-SX
processor handles the signaling requirements on each of 12 interface
channels. In addition to signaling, the 80386-SX performs many other
functions relating to digital signal processing operations.
The Intel 80386-SX microprocessor is described at pages 4-601 to 5-698 of
Intel Corporation's Microprocessors, Volume II databook (1992), which is
incorporated herein by reference. As described at pages 4-1034 to 4-1159
of that databook, the 82370 provides a high performance direct memory
access ("DMA") controller optimized for use with 80386 family
microprocessors, including the 80386-SX microprocessor. The 82370 DMA
controller can support up to 8 DMA channels for both 8-bit and 16-bit
devices, In the preferred embodiment, only the SBI ASIC and PCM ASIC use
the DMA channels. Both channels are treated as input/output devices, so
that the DMA controller of the 82370 provides only the memory address and
the read and write pulses.
A pulse code modulation bus, or "PCM highway" couples the DSP cells 20 to
the Trunk Interface Cards 13. The TIC's serve as analog-to-digital and
digital-to analog converters by converting incoming analog signals to
pulse code modulation digital data and transmitted data from storage
device 15 from digital data into analog signals.
The DLC card functions are divided into those that include processing of
the PCM samples and call control functions. Included in the first category
are tone detection, tone generation, voice compression and expansion,
voice detection and playback controls. The second set of functions involve
a higher level of control and are handled by the host processor on the
card, the 80386-SX chip. These functions include call setup and cleardown,
supervision of data transfers between DSP cells 20 and storage device 15,
and interpretation of call progress tones and DTMF tones detected by the
DSP cell.
Each DLC communicates with the main system processor (on CPU board 11) via
serial bus 16 controlled by serial bus interface application-specific
integrated circuit ("SBI ASIC") 26. The SBI ASIC, the details of which are
incidental to the present invention, provides a voice bus for transfer of
compressed voice samples between DLC 12 and system file card 14, and a
command bus for transfer of control and status messages between DLC 12 and
CPU board 11. Most transfers involve the movement of compressed voice
samples between system file card 14 and a DSP cell on the DLC. Transfers
between the serial bus interface and the 80386-SX are "fly-by" transfers,
that is, they do not involve the holding of data in an intermediate
location between read and write cycles. One skilled in the art will
recognize that these functions can be implemented in ASIC logic using for
example, conventional gate arrays.
The system clock to the 80386-SX is provided by a conventional programmable
array logic ("PAL") based state machine. The timing of clock and RESET
signals are synchronized to ensure reliable communications between the
80386-SX, 82370 , and DRAM, described hereinafter. The state machine is
conventional in design, except that a DRAM cycle is inhibited whenever a
dual-port RAM location is being accessed.
In a preferred embodiment, DRAM provides 1 Mbyte of address space, for
example, by using a conventional 1M.times.9 single in-line memory module
("SIMM") or two banks of four 256k.times.4 dual in-line pin ("DIP") DRAMS.
Code for the 80386-SX is downloaded to this DRAM by CPU board 11 upon
initialization of DLC 12. In addition, 32 k word electrically erasable
programmable read-only memory ("EEPROM") 24 is provided on the DLC, and
includes diagnostic and initialization functions for the 80386-SX that are
executed each time it is restarted. In a preferred embodiment, the EEPROM
may comprise a conventionally configured 27512.
Communications between the 80386-SX and each DSP cell are via dual-port
random access memory ("dual-port RAM") 28. This memory, which is 2 k by 16
bits is partitioned to allow for separate voice and control messages in
each direction. The dual-port RAM, depending upon the part selected, may
provide a facility to allow a processor on either side (the 80386-SX or
DSP cell) to interrupt the other processor. This can be achieved by having
the processors write to a specific location, so that the interrupted
processor clears the interrupt by reading the same location. A dual-port
RAM suitable for use in the present invention includes the 7132/7142.
Referring still to FIG. 3, a block diagram of DSP cell 20 constructed in
accordance with the present invention is described. The DSP cell comprises
a Texas Instruments TMS320C31 DSP microprocessor, 16 k by 16 bit static
random access memory ("SRAM") 29 and the above-mentioned 2 k by 16 bit
dual-port RAM 28. Texas Instrument Corporation's TMS320 series digital
signal processors are described, for example, in DIGITAL SIGNAL PROCESSING
APPLICATIONS With The TMS320 Family, Volume 3, Prentice Hall (1990,
Papamichalis editor). The TMS320 family of digital signal processors
provides highly specialized processors for multiply and add functions, so
that signal processing may take place on a real-time basis. The TMS320C31
selected for one embodiment of the present invention is driven by a 40 MHz
clock and executes out of a system memory comprising 16 k words of SRAM.
Unlike conventional implementations using this part, off-chip program
memory, off-chip data memory and I/O memory do not exist in separate
memory spaces. Instead, a flexible boundary is maintained between program
space and data space.
The DSP cell is responsible for providing tone detection and generation, as
well as voice compression and expansion for two channels of a TIC card, as
described hereinbefore. The data received by the DSP cells from the TICs
consists of voice, DTMF digits, call progression tones, test tones or
combinations of these tones. All out of band information (e.g., ringing,
off-hook, on-hook conditions) is passed directly to the 80386-SX on the
DLC. All information processed by the TMS320C31 chips is passed to the
80386-SX which either uses this information locally or passes it to CPU
board 11 via bus 16.
In one embodiment of the present invention, voice compression and expansion
is accomplished by the DSP cell using a variable bitrate subband coder
("VBSBC") voice compression algorithm, which produces 16 kbit/sec of data
for storage and retrieval. Of course, as will be recognized by those
skilled in the art of compression techniques, other compression algorithms
may be employed.
The TMS320C31 communicates with the 80386-SX controller via dual-port RAM
28. RAM 28 has separate blocks assigned for both incoming and transmitted
voice samples, and for control and status messages to be passed between
the controller and the DSP cell. Voice samples are transferred between the
DSP Cell and the TIC via the serial port of the TMS320C31. These voice
samples are encoded in companded format.
Clock control and framing pulses are provided for transfers of companded
voice samples between PCM highway 27 and DSP cell 20 by PCM ASIC chip 25,
which provides the interface between the DSP Cell and the PCM highway.
These transfers consist of signaling information for all 12 channels on a
TIC. The PCM ASIC provides the clock and the frame sync pulses to begin
transmission and reception of each sample. In addition, the PCM ASIC can
be programmed to discard a variable number of multiframes, for example,
1:544 msec, of signaling data, to reduce the burden on the 80386-SX and to
provide a variable scan rate of the line status of the channels. The PCM
ASIC, the details of which are incidental to the present invention, could
be implemented in ASIC logic by one skilled in the art by using, for
example, conventional gate arrays and programmable logic arrays.
Upon restart of the DLC, the reset line to the TMS320C31 is latched,
holding the processor in reset. The 80386-SX may reset each DSP cell
separately by providing six separate I/O addresses to reset and release
each DSP cell. The 80386-SX ensures that the contents of the dual-port RAM
are valid and then releases the processor from the reset state. Upon
completion of download of code from the 80386-SX to the dual-port RAM, the
TMS320C31 begins executing out of the dual-port RAM, since a RESET signal
sets the program counter to 0. As soon as normal operation begins, the
dual-port RAMs are used mainly as data memory by the TMS320C31.
Functions Of The Digital Line Card
The DLC of the present invention is designed to replace and improve certain
functionality of conventional analog line cards. In particular, the DLC
will provide the system with the ability to discriminate between voice and
data, to detect command signals included in the signal stream and to
switch between required modes of processing in response to those command
signals. The DLC also provides a capability to process incoming voice
information with any of several types of voice compression algorithms. To
achieve these functions, the TMS320C31 chip must be programmed to support
the activities, described hereinafter, during off-hook operation. In the
on-hook state, the TMS320C31 will be in an idle mode, primarily running
diagnostics and waiting for commands from the 80386-SX processor.
1. Monitoring Call Progress
Where the system detects that a telephone receiver has gone off-hook, the
DLC analyzes incoming signals and decodes various events before moving to
playback or record mode. Voice detection is used to recognize that an
outgoing call from the system has been initiated. An example of voice
detection is provided in copending and commonly assigned U.S. patent
application Ser. No. 07/625,369, filed Dec. 11, 1990, and entitled Methods
and Apparatus For Detecting Voice Information In Telephone Type Signals.
To achieve these functions, the DSP cell is programmed to receive and
expand a 64 kbps data stream generated by the TIC from logarithm data to
linear format and to output a 16 kbps data stream for storage.
The DLC is programmed to monitor for call progression tones and
multifrequency (MF) digits by reporting envelope data to the 80386-SX
processor. The MF digits are used for system communication in a manner
analogous to the use of DTMF digits by the caller. The specific envelope
filters are preset by a command from the 80386-SX; the 80386-SX then
post-processes the envelope information to extract out call progression
tones and MF digits. This envelope data also contains a time stamp and the
results of a voice detection test.
The DLC also is programmed with the capability to decode DTMF digits and to
report these command digits to the 80386-SX processor. One such scheme is
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