U.S. patent application number 09/734790 was filed with the patent office on 2001-08-09 for method and apparatus for dtmf signaling on compressed voice networks.
Invention is credited to Beyda, William J., Gilbert, Leroy E., Jacobi, Eli, Kozdon, Peter, Shaffer, Shmuel.
Application Number | 20010012305 09/734790 |
Document ID | / |
Family ID | 21948211 |
Filed Date | 2001-08-09 |
United States Patent
Application |
20010012305 |
Kind Code |
A1 |
Kozdon, Peter ; et
al. |
August 9, 2001 |
Method and apparatus for DTMF signaling on compressed voice
networks
Abstract
A method of transmitting DTMF signals over a compressed computer
network (24) comprises sending a packet containing a compressed
DTMF signal followed by a confirmation packet. The confirmation
packet preferably comprises an uncompressed DTMF signal which is
transmitted on the same logical channel as the packets that
represent voice signals. To detect the DTMF signal transmitted, a
telephony Internet server (28) decompresses packets as they are
received. If a packet appears to contain a compressed DTMF signal,
the telephony Internet server looks for the presence of the
confirmation packet before processing the previously received
packet as a DTMF signal. In an alternative embodiment, the
confirmation packet comprises a code that represents a DTMF signal.
The packets that represent the voice signal and the code
representing the DTMF signal are sent on separate virtual channels
of the same logical channel. At a receiving end, data on one
channel is directed by a separation logic block (114) to a speech
decompressor (116) while another channel is directed to a DTMF
signal generator (118) that generates a DTMF signal when a
corresponding code is detected. The outputs of either the speech
decompressor or the DTMF signal generator are applied to a
receiving telephone (124).
Inventors: |
Kozdon, Peter; (Santa Clara,
CA) ; Jacobi, Eli; (Palo Alto, CA) ; Shaffer,
Shmuel; (Palo Alto, CA) ; Beyda, William J.;
(Cupertino, CA) ; Gilbert, Leroy E.; (Wellington,
FL) |
Correspondence
Address: |
Siemens Corporation
Intellectual Property Department
186 Wood Avenue South
Iselin
NJ
08830
US
|
Family ID: |
21948211 |
Appl. No.: |
09/734790 |
Filed: |
December 11, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09734790 |
Dec 11, 2000 |
|
|
|
09047301 |
Mar 24, 1998 |
|
|
|
Current U.S.
Class: |
370/525 ;
370/526; 379/283; 379/386 |
Current CPC
Class: |
H04Q 2213/13034
20130101; H04L 2012/6481 20130101; H04Q 2213/1322 20130101; H04Q
2213/13093 20130101; H04L 2012/6443 20130101; H04Q 2213/13196
20130101; H04M 7/1295 20130101; Y10S 379/90 20130101; H04Q
2213/13176 20130101; H04Q 2213/13204 20130101; H04L 2012/6472
20130101; H04Q 2213/13405 20130101; H04Q 2213/13174 20130101; H04Q
3/0025 20130101; H04L 9/40 20220501; H04L 2012/6486 20130101; H04Q
2213/13396 20130101; H04Q 2213/13377 20130101; H04Q 2213/13389
20130101; H04L 12/6418 20130101 |
Class at
Publication: |
370/525 ;
379/283; 370/526; 379/386 |
International
Class: |
H04M 003/00; H04M
005/00; H04J 003/12 |
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A method of transmitting dual tone multi-frequency (DTMF)
signals on a computer network, comprising: receiving a telephone
signal to be transmitted on the computer network; determining
whether the telephone signal to be transmitted is a DTMF signal;
digitizing the received telephone signal and dividing the digitized
signal into a series of packets; compressing the series of packets;
transmitting the compressed packets on the computer network; and if
a compressed packet contains a DTMF signal, then transmitting a
confirmation packet after the packet that contains the compressed
DTMF signal.
2. The method of claim 1, wherein the step of transmitting the
confirmation packet comprises the step of: transmitting a packet
containing an uncompressed DTMF signal.
3. The method of claim 1, wherein the step of transmitting the
confirmation packet comprises the step of: transmitting one or more
additional packets containing a compressed DTMF signal.
4. The method of claim 1, wherein the packets and the confirmation
packet are transmitted on a same logical channel on the computer
network.
5. The method of claim 1, wherein the packets and the confirmation
packet are transmitted on different virtual channels of the same
logical channel on the computer network.
6. The method of claim 1, further comprising determining if a DTMF
signal has been received on the computer network by: receiving a
compressed packet on the computer network; determining whether the
packet received contains a compressed DTMF signal, and if so,
receiving a subsequent packet on the computer network; and
determining whether the subsequent packet is the confirmation
packet that indicates that the previous packet contains a
compressed DTMF signal.
7. The method of claim 6, further comprising the step of: applying
a DTMF signal to a voice mail system if the subsequent packet
indicates that the previous packet contains a compressed DTMF
signal.
8. The method of claim 6, further comprising the step of: applying
a DTMF signal to a voice recognition unit if the subsequent packet
indicates that the previous packet contains a compressed DTMF
signal.
9. A method of transmitting DTMF signals on a computer network,
comprising the steps of: receiving a telephone signal including
voice signals and DTMF signals; simultaneously compressing the
received telephone signal and analyzing the received telephone
signal for the presence of a DTMF signal; generating one or more
codes representing the DTMF signal if a DTMF signal is detected;
and transmitting the compressed telephone signal and the one or
more codes representing the DTMF signal on the computer
network.
10. The method of claim 9, wherein the step of transmitting the
compressed telephone signal and the one or more codes representing
the DTMF signal are sent on the same logical channel
11. The method of claim 9, wherein the step of transmitting the
compressed telephone signal and the one or more codes representing
the DTMF signal, comprises: transmitting the compressed telephone
signal on a first virtual channel of a multichannel real time
protocol data stream; and transmitting the one or more codes
representing the DTMF signal on a second virtual channel of a
multichannel real time protocol data stream.
12. The method of claim 9, further comprising the steps of:
receiving the compressed telephone signals and the one or more
codes representing the DTMF signal from the computer network;
simultaneously decompressing the compressed telephone signals and
detecting whether one or more codes representing DTMF signals have
been received from the computer network; generating DTMF signals if
one or more codes representing the DTMF signals are received; and
supplying either the decompressed telephone signals or the
generated DTMF signals to a receiver.
13. The method of claim 12, wherein the step of supplying either
the decompressed telephone signals or the generated DTMF signals to
a receiver comprises the steps of: supplying the decompressed
telephone signals to the receiver if the one or more codes
representing the DTMF signals are not detected; or supplying the
generated DTMF signals to a receiver if one or more codes
representing the DTMF signals are detected.
14. A communication system for transmitting telephone signals
between a sending telephone unit and a receiving telephone unit,
comprising: a sending telephone unit that generates telephone voice
signals including one or more DTMF signals; a splitter that
receives the telephone voice signals and DTMF signals from the
sending telephone unit and supplies the telephone voice signals and
DTMF signals to a speech compressor that compresses the telephone
voice signals and DTMF signals and to a DTMF signal detector that
detects the presence of a DTMF signal and creates one or more codes
that represent a detected DTMF signal; and a multiplexer that
receives an output of the speech compressor and an output of the
DTMF signal detector and transmits the compressed telephone voice
signals and one or more codes representing the DTMF signals on a
single channel of a computer network.
15. The communication system according to claim 14, further
comprising: a channel splitter that receives the compressed
telephone voice signals and the one or more codes representing the
DTMF signals from the computer network; a speech decompressor that
receives the compressed telephone voice signals from the channel
splitter and decompresses the telephone signals; a DTMF signal
generator that receives the one or more codes representing the DTMF
signals from the channel splitter and generates a DTMF signal
corresponding to the one or more codes representing the DTMF
signals received; and a switch that couples the decompressed
telephone signals produced by the speech decompressor or the DTMF
signals generated by the DTMF signal generator to the receiving
telephone unit.
16. The communication system according to claim 15, wherein the
receiving telephone unit comprises a voice recognition unit.
17. The communication system according to claim 15, wherein the
receiving telephone unit comprises an integrated voice response
unit.
18. The communication system according to claim 15, wherein the
computer network comprises the Internet.
19. The communication system according to claim 15, wherein the
computer network comprises a local area computer network.
20. The communication system according to claim 15, wherein
multiplexer places the compressed telephone signals on a first
channel of a real time protocol data stream and the one or more
codes representing the DTMF signals on a second channel of the real
time protocol data stream.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to communication systems in
general, and in particular to communication systems that transmit
telephone signals over compressed computer networks.
BACKGROUND OF THE INVENTION
[0002] As an alternative to placing all telephone calls through the
public switched telephone network, many companies are utilizing the
excess capacity in their computer networks to carry a portion of
their telephone calls. This is advantageous because the company
does not have to pay for each telephone call individually. However,
because such networks were not specifically designed for
telecommunication, there are some inherent problems that occur when
transmitting telephone signals over such networks.
[0003] One common problem with telephone calls that are routed over
computer networks occurs when a call is placed to a system or
device that detects and responds to dual tone multi-frequency
(DTMF) signals commonly referred to as Touch-tone.TM. signals. Such
systems may include voice mail systems that allow users to store
and retrieve messages or voice recognition units (also called
integrated voice response units) that are programmed to retrieve
information after entering one or more Touch-tone signals on a
telephone keypad. One example of a voice recognition unit is an
automatic banking response system of the type commonly provided by
banks to allow users to access their accounts over the
telephone.
[0004] When telephone signals are transmitted over a computer
network, such as a local area network (LAN) or wide area network
like the Internet, the telephone voice signals, as well as the DTMF
signals are digitized, organized into a number of data packets, and
compressed prior to transmission. Upon receipt, these data packets
are decompressed and analyzed to reconstruct the original telephone
signals. When a DTMF signal is compressed, transmitted over the
computer network, and decompressed, the result is no longer a set
of pure sinusoidal tones having predefined frequencies. Instead,
the tones become distorted and can therefore be difficult to detect
with a digital signal processor. As such, many communication
systems do not support sending DTMF signals over compressed
computer networks. Alternatively, systems are required to store the
telephone number of the voice mail or integrated voice response
systems that can be accessed within a network. All calls to these
systems are routed over uncompressed networks. The complexities of
routing a call on either an uncompressed or compressed network,
depending on the destination, is generally inefficient.
[0005] Given the shortcomings in the prior art, there is a need for
a method of reliably sending DTMF signals over compressed computer
networks that does not require the use of additional channels or
monitoring the destination called.
SUMMARY OF THE INVENTION
[0006] The present invention is a method of transmitting DTMF
signals over a computer network. A received telephone signal is
digitized, divided into a series of packets, and compressed using a
conventional compression algorithm. The compressed packets are then
transmitted on a data network. As the telephone signal is being
digitized and divided into packets, it is continually analyzed to
detect the presence of a DTMF signal. Upon the detection of a DTMF
signal, an additional confirmation packet is inserted into the
stream of packets and transmitted after the compressed packet that
represents the DTMF signal. According to one embodiment of the
invention, the confirmation packet comprises the uncompressed DTMF
signal.
[0007] At a receiving end, packets are decompressed and analyzed to
determine if they may represent a DTMF signal. If it appears that a
packet containing a compressed version of a DTMF signal has been
received, a receiving station looks for the confirmation packet. If
the confirmation packet is present, the receiving station knows
that a DTMF signal was received and the DTMF signal is processed
accordingly. If the confirmation packet is not detected, then the
compressed packet in question is treated as a voice signal.
[0008] According to another embodiment of the present invention, a
telephone signal to be transmitted over a computer data network is
simultaneously compressed and analyzed for the presence of a DTMF
signal. If a DTMF signal is detected, a confirmation packet
comprising a code that represents the DTMF signal is produced. The
code representing the DTMF signal and the compressed telephone
voice signals are transmitted on separate virtual channels of the
same logical channel to a receiver over a computer network.
[0009] At the receiver, the received signals on each virtual
channel are split such that one channel is decompressed while
packets on the other channel are analyzed for the presence of the
code representing the DTMF signals. If no codes are detected, the
decompressed telephone signals are applied to a receiving
telephone. If a code representing a DTMF signal is detected, a *
corresponding DTMF signal is recreated and applied to the receiving
telephone.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The foregoing aspects and many of the attendant advantages
of this invention will become more readily appreciated as the same
becomes better understood by reference to the following detailed
description, when taken in conjunction with the accompanying
drawings, wherein:
[0011] FIG. 1 is a block diagram of a communication system that
transmits telephone signals on a compressed data network;
[0012] FIG. 2 is an alternative embodiment of a communication
system that transmits telephone signals on a compressed data
network;
[0013] FIG. 3 is a block diagram of a system for transmitting DTMF
telephone signals on a compressed data network according to the
present invention;
[0014] FIG. 4 is a flow chart of the steps performed by the present
invention in order to transmit DTMF signals on a compressed data
network; and
[0015] FIGS. 5A and 5B are flow charts of the steps performed by
two alternative embodiments of the present invention in order to
receive DTMF signals that are transmitted on a compressed data
network.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] The present invention is a method of reliably transmitting
DTMF signals over a compressed data network such as a local area
network (LAN) or a wide area network, like the Internet.
[0017] FIG. 1 illustrates a typical communication system 10 that
carries a telephone call placed from one or more source telephones
12 to one or more destinations 14, which may comprise another
telephone or computerized device such as a voice mail system or
voice recognition unit. For systems that support many users, the
source telephones 12 are generally connected to a private branch
exchange (PBX) 16 that routes a call through a public switched
telephone network (PSTN) 18. Also connected to the PSTN 18 is a
private branch exchange 20 that is connected to one or more
destination telephones, voice mail systems or voice recognition
units 14.
[0018] As indicated above, a caller wishing to place a call from
one of the source telephones to a destination is charged each time
a telephone call is placed over the PSTN 18. In order to reduce the
cost of communication services, it is possible to place the calls
from a source to the destination on an alternate route. For
example, telephone calls can be placed on a computer network 24
that is typically used to transmit computer data from one point to
another. The computer network 24 is typically a LAN or wide area
network such as the Internet. To transmit a telephone call on the
computer network 24, the private branch exchanges 16 and 20 are
each connected to a telephony Internet server 26 and 28,
respectively. Telephone calls can be routed from the private branch
exchange 16 through the telephony Internet server 26, where they
are transmitted over the computer network 24 to arrive at the
telephony Internet server 28 that is connected to the private
branch exchange 20. The private branch exchange 20 then routes the
telephone signals received to the destination telephone, voice mail
system or voice recognition unit 14, thereby bypassing the public
switched telephone network.
[0019] Telephone calls placed over the computer network 24 are not
typically free because the communication lines that comprise the
computer network 24 are generally leased. However, the excess
capacity of these lines can be utilized without paying additional
fees. Whether a telephone call is placed on the PSTN 18 or on the
computer network 24, may be determined based on a variety of
factors including the capacity of the computer network, the urgency
of the call, the fidelity required, etc.
[0020] As described above, one of the problems associated with
transmitting telephone signals over a computer network 24 such as
the Internet, is the ability of a decoder to detect dual tone
multi-frequency (DTMF) signals that are compressed and transmitted
over such a network. In the example shown in FIG. 1, the telephony
Internet server 28, that is associated with the destination of the
telephone call, receives compressed data packets and decompresses
them to recreate the original telephone signals. If a user presses
a key on a keypad of the source telephone 12, the DTMF signal
generated is digitized, packetized, and compressed by the telephony
Internet server 26 before being transmitted over the computer
network 24. Upon receipt, the de-compressed DTMF signal will not
maintain its spectral purity so that a digital signal processor at
the destination cannot determine whether the received packet is
indeed representative of a DTMF signal. Therefore, in the past,
users of a source telephone 12 have had difficulty controlling
systems, such as a voice mail system or voice recognition unit,
using DTMF signals when the call is routed over the compressed
computer network 24.
[0021] FIG. 2 illustrates another communication system in which a
telephone call is routed over a computer network. In this example,
the source comprises a computer system 30 that includes a central
processing unit 32, keyboard 34, pointing device such as a mouse
36, and speakers 38. Alternatively, the source may comprise an
Internet Protocol telephone which is designed specifically for
transmitting telephone signals over computer networks.
[0022] To generate the communication signals, the user speaks into
a microphone or headset 40 that is connected to a sound card (not
shown). DTMF signals are generated when the user presses the
numbered keys on the keyboard 34. The voice signals received from
the microphone 40 are digitized, packetized, compressed and
transmitted on a local area network 50 by the central processing
unit. If the call is to be transmitted over multiple LANs, or on a
wide area network, the local area network 50 may be coupled to a
router computer 52 that transmits the digitized, packetized and
compressed telephone signals to another network such as the
Internet 54.
[0023] At the destination, a telephony Internet server 56, which is
also coupled to the Internet 54, receives the compressed telephone
signals and decompresses them for supply to a private branch
exchange 58. The private branch exchange is connected to a
destination telephone, voice mail system or voice recognition unit
60 as described above. Again, the problem with the communication
system shown in FIG. 2 is that the destination voice mail system,
voice recognition unit, or PBX, has difficulty determining when
touch-tone signals are generated by the source computer system 30
due to the nature of the compression performed prior to
transmission of the packets on the local area network 50 and
Internet 54.
[0024] FIG. 3 is a block diagram of a system for transmitting DTMF
signals on a compressed voice network according to the present
invention. The communication system 100 comprises a sending
telephone or computer 102 that transmits telephone signals to a
destination or receiving telephone system 124. The receiving
telephone system 124 may be a conventional telephone used for voice
communications or may comprise a voice recognition unit, integrated
voice response unit or other computer that responds to DTMF
signals.
[0025] To transmit telephone signals from the sending telephone 102
to the receiving telephone 124, signals from the sending telephone
are applied to a splitter 104. The splitter 104 supplies the
telephone signals to a pair of digital signal processors (DSP's)
106 and 108. The first digital signal processor 106 operates as a
speech compressor and runs a speech compression algorithm that
analyzes the telephone signals applied and compresses them
according to techniques well known in the art. The second digital
processor 108 operates as a DTMF signal detector and also receives
the telephone signals produced by the sending telephone 102. The
second digital signal processor 108 analyzes the telephone signals
received for the presence of one or more DTMF signals. Upon
detecting a DTMF signal, the digital signal processor 108 produces
one or more codes that indicate to the receiving telephone that a
DTMF signal is being transmitted. For example, in one embodiment of
the invention, the second digital signal processor 108 generates a
confirmation packet that comprises either a second compressed DTMF
signal or a packet containing an uncompressed DTMF signal. The
confirmation packet is transmitted immediately after the packet
containing the compressed DTMF signal that is produced by the first
digital signal processor 106. The original data packet containing
the compressed DTMF signal and the confirmation packet are combined
by a combination logic circuit 110 so that the two packets are
transmitted on the same logical channel over the computer network
to the destination telephone.
[0026] In an alternative embodiment of the invention, the second
digital signal processor 108 produces a numeric code that
represents the DTMF signal detected. For example, if a user presses
the numeral 4 on their telephone keypad, the second digital signal
processor 108 may produce one or more binary codes having a value
of 004. However, any coding scheme that matches a code to a
particular DTMF signal can be used. If no DTMF signal is detected
by the second digital signal processor 108, then either no data or
one or more null codes are produced.
[0027] The compressed voice signals produced by the first digital
signal processor 106 and the codes produced by the second digital
signal processor 108 are applied to the combination logic circuit
110 that inserts the data onto a logical channel for transmission
on a computer network 112 such as the Internet. In the second
embodiment of the invention, the combination logic circuit 110
places the compressed telephone signals and codes representing the
DTMF signals produced by the digital signal processors 106 and 108
onto separate left and right virtual channels of a real time
protocol (RTP) data stream.
[0028] At the destination, packets received from the computer
network 112 are applied to a separation logic circuit 114 that
supplies the data received from the computer network 112 to a pair
of digital signal processors 116 and 118. The digital signal
processor 116 operates as a speech decompressor and runs a speech
decompression algorithm which converts the compressed speech
received on the computer network 112 back to uncompressed speech.
In addition, the speech decompression algorithm 116 attempts to
decompress the DTMF signals that were compressed by the digital
signal processor 106. However, because these codes do not represent
compressed speech, the output of the digital signal processor 116
for these data packets will be meaningless.
[0029] When the compressed speech signals and the codes
representative of the DTMF signals are transmitted on separate
virtual channels, the digital signal processor 118 operates as a
DTMF signal generator and analyzes each of the packets received on
the other channel of the RTP data stream for codes that are
indicative of a DTMF signal. Upon detection of such a code, the
digital signal processor 118 recreates or synthesizes an
appropriate DTMF signal for supply to the receiving telephone
124.
[0030] The outputs of the digital signal processors 116 and 118 are
supplied to a switch 120. The switch is selectable between a first
position wherein the output of the digital signal processor 116,
comprising the decompressed speech, is applied to the receiving
telephone 124. In the second position, the output of the digital
signal processor 118, comprising the recreated DTMF signals, is
supplied to the receiving telephone 124. The position of the switch
is controlled by a switching logic circuit 122 that receives a
signal from the digital signal processor 118. Upon the detection of
a code indicative of a DTMF signal, the digital signal processor
118 signals the switching logic circuit 122 in order to change the
position of the switch 120 such that the recreated DTMF signals are
supplied to the receiving telephone 124. When the digital signal
processor 118 no longer detects the codes indicative of a DTMF
signal, the digital signal processor 118 signals the switching
logic circuit 122 to move the position of the switch 120 such that
the output of the decompressed speech produced by the digital
signal processor 116 is applied to the receiving telephone 124.
[0031] If the system indicates the presence of a DTMF signal by
sending a confirmation packet on the same channel as the voice
data, the switch 120 remains connected to the output of the digital
signal processor 116. The digital signal processor 116 analyzes
each packet for the presence of a possible DTMF signal. If such a
packet is received, the following packet is analyzed to confirm the
presence of the DTMF signal. If no confirmation packet is received,
the previous packet is treated as voice data.
[0032] The communication system 100 described above allows the
transmission of DTMF signals without the use of additional
uncompressed channels. In addition, because the data is transmitted
on the same logical channel, synchronization between the speech and
signaling is maintained without any increases in bandwidth
required. Finally, the system can be made symmetrical whereby voice
and DTMF signals produced by the telephone 124 for transmission to
the telephone 102 can also be split and applied to speech
compression and DTMF signal detecting digital signal processors
before being transmitted on the computer network.
[0033] FIG. 3 illustrates a series of steps performed by a
telephony Internet server to transmit a DTMF signal on a compressed
computer network. Beginning with a step 150, the telephony Internet
server determines whether a stream of telephone signals (including
voice and DTMF signals) is received. If not, processing returns to
step 150 until such a stream of telephone signals is received.
Assuming that a telephone signal is being received, the telephony
Internet server packetizes, compresses and transmits the signals on
the computer network at a step 152. At a step 154, the telephony
Internet server determines whether a DTMF signal was received. This
is typically performed using the digital signal processor 108
described above that continually analyzes the received telephone
signals for a sinusoidal signal having a pair of predefined
frequencies. If a DTMF signal is detected, a confirmation packet is
transmitted at a step 156. As indicated above, the confirmation
packet may comprise an additional compressed or uncompressed DTMF
signal that is transmitted on the same logical channel immediately
after the packet that contains the compressed DTMF signal.
Alternatively, a code representing the DTMF signal can be sent on a
separate virtual channel to the receiving telephony Internet
server.
[0034] FIG. 5A illustrates the series of steps performed by a
telephony Internet server in order to accurately detect the
transmission of a DTMF signal when a confirmation packet is
transmitted on the same channel as the compressed voice data.
Beginning with a step 170, the telephony Internet server determines
whether a data packet has been received from the computer network.
If not, processing returns to step 170 until such a packet is
received. Once a packet has been received, processing proceeds to a
step 172, wherein the received packet is decompressed. At a step
174, a digital signal processor in the telephony Internet server
determines whether the decompressed packet may represent a DTMF
signal. If not, the received decompressed packet is processed as a
conventional voice signal at a step 176.
[0035] Assuming the answer to step 174 is yes, and the received
packet may represent a possible DTMF signal, the decompressed
packet is held at a step 180 and the telephony Internet server
begins looking for the confirmation packet to be transmitted.
[0036] Beginning at a step 182, the telephony Internet server waits
for the next data packet to be received. Once the next data packet
is received, processing proceeds to a step 184, wherein it is
determined if the subsequent data packet received contains an
uncompressed DTMF signal. If so, the latest packet is processed as
a DTMF signal at a step 186, and the previously held packet is
ignored at a step 188.
[0037] If the answer to step 184 is no and the subsequent packet
does not contain an uncompressed DTMF signal, the packet that was
held at step 180 is processed as a conventional voice signal at a
step 190. The subsequent data packet is then decompressed at a step
192 and processing then returns to the step 174 to determine
whether the subsequent packet may contain a possible compressed
DTMF signal. The steps shown in FIG. 5A continue as long as packets
of telephone signals are received from the compressed computer
network.
[0038] FIG. 5B illustrates the steps performed by the present
invention when the voice packets and codes representative of DTMF
signals are transmitted on separate virtual channels of the same
logical channel. Beginning with a step 200, the receiving telephony
Internet server determines if a data packet has been received. If
so, processing proceeds to a step 202 where the packets on each
virtual channel (referred to as channel A and channel B) are
separated. At a step 204, the receiving telephony Internet server
determines whether the packet received on the virtual channel B is
representative of a DTMF signal. If so, the packet is treated as a
DTMF signal. If the answer to step 204 is no, then the packet
received on virtual channel A is decompressed at a step 208 and
processed as voice data at a step 210.
[0039] As can be seen from the above, the present invention allows
systems such as voice mail systems or voice recognition units that
are operated by DTMF signals to be accessed from computer networks
that carry compressed data. As such, voice mail systems or voice
recognition units can be accessed from local area or wide area
networks such as the Internet.
* * * * *