Title: Device capable of accommodating existing voice terminals
Abstract: A line unit is connected to an integrated voice/data switching unit by a connection line and includes a plurality of extension interfaces customary with a PBX (Private Branch Exchange). The extension interfaces each accommodate telephones or similar voice terminals and connect them to the switching unit. Each extension interface is connected to a particular packet processing unit by a dual port memory and a 2M highway interface. The line unit switches frame signals subjected to TDM (Time Division Multiplexing) and packets received from a network on a connection line and interchanges voice packets when a communication path is set up.
Patent Number: 6,839,341 Issued on 01/04/2005 to Nakajima
| Inventors:
|
Nakajima; Yasunori (Tokyo, JP)
|
| Assignee:
|
Oki Electric Industry Co., Ltd. (Tokyo, JP)
|
| Appl. No.:
|
534634 |
| Filed:
|
March 27, 2000 |
Foreign Application Priority Data
| Jun 17, 1999[JP] | 11-170401 |
| Current U.S. Class: |
370/352; 370/401; 370/442 |
| Intern'l Class: |
H04L 012/66; H04L012/56; H04B007/212 |
| Field of Search: |
370/352,401,336,347,354,360,412,442
|
References Cited [Referenced By]
U.S. Patent Documents
| 4723238 | Feb., 1988 | Isreal et al. | 370/352.
|
| 4771425 | Sep., 1988 | Baran et al. | 370/458.
|
| 5251206 | Oct., 1993 | Calvignac et al. | 370/352.
|
| 6259691 | Jul., 2001 | Naudus | 370/352.
|
| 6269095 | Jul., 2001 | Neubauer et al. | 370/352.
|
| 6381238 | Apr., 2002 | Hluchyj | 370/352.
|
| 6515996 | Feb., 2003 | Tonnby et al. | 370/401.
|
| 6643291 | Nov., 2003 | Yoshihara et al. | 370/395.
|
| Foreign Patent Documents |
| 0 640 927 | Mar., 1995 | EP.
| |
| 6386/1994 | Jan., 1994 | JP.
| |
| 226750/1995 | Aug., 1995 | JP.
| |
| 09/191324 | Jul., 1997 | JP.
| |
Primary Examiner: Pezzlo; John
Assistant Examiner: Tsegaye; Saba
Attorney, Agent or Firm: Rabin & Berdo, P.C.
Claims
What is claimed is:
1. A device for accommodating a plurality of voice terminals for voice
communication and connecting said voice terminals to a switching unit,
said device comprising:
a plurality of digital extension interface circuits each accommodating a
plurality of digital voice terminals of said plurality of voice terminals
and controlling calls originating from and calls incoming to said
plurality of digital voice terminals, said plurality of digital extension
interface circuits connecting said plurality of digital voice terminals to
first time division multiplexing communication highway paths;
a plurality of analog extension interface circuits each accommodating a
plurality of analog voice terminals of said plurality of voice terminals
and controlling calls originating from and calls incoming to said
plurality of analog voice terminals, said plurality of analog extension
interface circuits connecting said plurality of analog voice terminals to
second time division multiplexing communication highway paths;
a plurality of storages connected to said plurality of digital extension
interface circuits and said plurality of analog extension interface
circuits for storing frame signals transferred via an associated one of
said first or second time division multiplexing communication highway
paths;
a plurality of packet processing circuits, each connected to an associated
one of said plurality of storages via a respective third time division
multiplexing communication highway path, for converting the frame signal
to packets and for converting packets to frame signals;
a transferring circuit interfacing with said plurality of packet processing
circuits and with a local area network via said switching unit for
switching and transferring the packets; and
a synchronization controller for controlling synchronization between said
plurality of digital and analog interface circuits and said plurality of
packet processing circuits.
2. A device in accordance with claim 1, wherein said switching unit is a
packet switching unit that is connected to said transferring circuit, said
device being capable of communicating with other voice terminals
accommodated by said packet switching unit.
3. A device in accordance with claim 1, wherein each of said plurality of
digital voice terminals accommodates a digital key telephone.
4. A device in accordance with claim 1, wherein each of said plurality of
analog voice terminals accommodates an analog telephone.
5. A device in accordance with claim 1, further comprising a trunk circuit
connected to an office line.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for accommodating voice terminals
for voice communication in a switching unit.
2. Description of the Background Art
Today, studies and developments are under way for connecting, e.g.,
telephones dealing with voice communication and G3 facsimile apparatuses
to a local area network (LAN) mainly dealing with data communication in
order to implement integrated voice/data communication. For example, IP
(Internet Protocol) telephones and personal computers or similar exclusive
terminals may be connected, via network cables, to an integrated
voice/data switching unit connected to a LAN. The IP telephone sets are
capable of sending and receiving data in the form of IP packets. In such a
configuration, the telephones and exclusive terminals are capable of
holding voice communication with equipment also connected to the LAN.
An IP telephone, for example, includes a control circuit for assembling and
disassembling voice packets and control packets, a multifunction CODEC, an
input section including numeral keys, a display device including LEDs
(Light Emitting Diodes) and an LCD (Liquid Crystal Display), a
transmitter/receiver, and a LAN interface. This kind of telephone is
capable of interchanging IP packets produced by packetizing a voice signal
with an IP network and is a promising new voice communication apparatus.
On the other hand, a digital PBX (Private Branch Exchange) accommodates
voice communication terminals including existing telephones belonging to a
conventional telephone network. The digital PBX includes extension
interfaces each designed for a particular terminal accommodated therein
and provides various kinds of voice communication services. The terminals
connected to the PBX may be key telephones by way of example. It follows
that various kinds of services are expected even with IP telephones.
However, substituting the above integrated voice/data switching unit
accommodating IP telephones and other terminals for all of an existing
digital PBX system and analog telephone equipment is not desirable from
the work and equipment cost standpoint although it will successfully
integrate the entire voice communication base into a data communication
network. Specifically, a conventional key telephone, for example, does not
include a LAN interface and cannot be easily connected to an integrated
voice/data switching unit. As a result, when an integrated voice/data
switching unit is actually operated, all existing telephones lacking a LAN
interface become useless.
To accommodate existing telephones in an integrated voice/data switching
unit, it is necessary to newly develop and produce subscriber circuits,
trunks or similar interface circuits in accordance with the telephones and
switching unit by exclusive designing. This not only further increases the
development cost, but also obstructs the effective use of existing
equipment. Specifically, various line packages included in a digital PBX
for accommodating the telephones cannot be used at all despite that analog
telephones and interfaces including office lines and exclusive lines are
unchanged.
As stated above, an efficient system implementing integrated voice/data
communication with an integrated voice/data switching unit cannot be
easily constructed with existing terminals and existing line packages.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a device
allowing existing telephones and line packages to be connected thereto and
accommodated in an integrated voice/data switching unit.
A device for accommodating a voice terminal for voice communication and
connecting it to a switching unit of the present invention includes a
plurality of connecting circuits to which a plurality of interface
circuits each accommodating a plurality of voice terminals and controlling
the call origination and call incoming thereof are respectively connected
by time division multiplexing communication paths. A plurality of storages
are respectively connected to the connecting circuits each for storing a
frame signal transferred via associated one of the time division
multiplexing communication paths. A plurality of packet processing
circuits are respectively connected to the storages each for converting
the frame signal and packets to each other. A transferring circuit is
connected to the packet processing circuits for switching and transferring
the packets. A synchronization controller controls synchronization between
the interface circuits and the packet processing circuits.
BRIEF DESCRIPTION OF THE DRAWINGS
The objects and features of the present invention will become more apparent
from the consideration of the following detailed description taken in
conjunction with the accompanying drawings in which:
FIG. 1 is a block diagram schematically showing a line accommodating device
embodying the present invention;
FIG. 2 is a schematic block diagram showing a specific integrated
voice/data switching system including the illustrative embodiment;
FIG. 3 is a schematic block diagram showing a specific configuration of a
packet processing circuit included in the illustrative embodiment;
FIG. 4 is a schematic block diagram showing a specific configuration of a
digital key telephone;
FIG. 5 is a schematic block diagram showing a specific configuration of an
IP telephone set; and
FIG. 6 is a schematic block diagram showing a typical configuration of a
server.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 2 of the drawings, an integrated voice/data switching
system to which a voice terminal accommodating device embodying the
present invention is applied is shown. As shown, the switching system,
generally 10, includes an integrated voice/data switching unit 18 having a
LAN switch (LAN-SW) 20. A server 22 and an IP telephone set 24 are
connected to the switching unit 18 by 10 Mbps (megabits per second),
Ethernet LAN network cables 200 and 202, respectively. A line unit or line
accommodating device 16 is also connected to the switching unit 18 by a
100 BASE Ethernet network cable 204. The system 10 sends IP packets
including voice data and received from various equipment accommodated
therein to desired destinations.
Digital key telephones (KTSs; Key Telephone Systems) 12 and analog
telephones (TELs) 14 belonging to an existing PBX telephone system are
connected to the integrated voice/data switching unit 18 by cords 206 and
208, respectively. The system 10 may not only be newly installed in an
office or similar private facility, but also be added to a telephone
system existing in an office or even be substituted for an existing
switching unit. Part of the system 10 not directly relevant to the
understanding of the present invention is not shown and will not be
described specifically. It is to be noted signals appearing in the system
10 are designated by the reference numerals attached to connection lines
on which they appear.
FIG. 1 shows a specific configuration of the line unit 16 specifically. As
shown, digital extension interfaces (EX I/Fs) 30a each accommodating a
plurality of digital KTSs 12, FIG. 2, and analog EX I/Fs 30b each
accommodating a plurality of analog TELs 14, FIG. 2, are connected to the
line unit 16 by 2M (2 megabits per second highways, 2MHW hereinafter) 32
belonging to a TDM (Time Division Multiplexing) communication path. The
digital EX I/Fs 30a and analog EX I/Fs 30b are implemented as two kinds of
line packages. A signal input/output 32 of each EX I/F 30a or 30b is
connected to one port of a particular dual port RAM (Random Access Memory;
DP RAM hereinafter) 34. The other port of each DP RAM 34 is connected to a
particular packet processing circuit 38 by 2MHWs 36.
As shown in FIG. 3, each EX I/F, labeled 30, is connected to the associated
packet processing circuit 38 by a bus 40. The EX I/F 30 sends information
received from the telephones and including the telephone numbers of
destinations to the packet processing circuit 38 via a control line 40. In
response, the packet processing circuit 38 outputs to a connection line 50
a control packet containing the above information and voice packets
produced by packetizing frames input from the associated DP RAM 34. The
connection line 50 is connected to a LAN I/F 52 by star-type network
connection or bus-type network connection. When the packet processing
circuit 38 receives packets addressed thereto from the LAN I/F 52 via the
connection line 50, it disassembles the packets into frames and outputs
the frames to the 2MHW 36. As shown in FIG. 1, the line unit 16 has a
plurality of signal processing circuits each being made up of the EX I/F
30, DP RAM 34, and voice packet processing circuit 38.
Each EX I/F 30 includes a connection interface applicable to a conventional
PBX and multiplexes voice frames and control frames by TDM and
interchanges such frames with the DP RAM 34 via the 2MHW 32. In the
illustrative embodiment, the communication paths 32 and 36 are implemented
by, e.g., a 2M highway interface for multiplexing 64 kbps (kilobits per
second) of information with thirty-two channels. Also, the EX I/F 30
generates a frame signal having time slots TS0 through TS 31 every 125
microseconds. The frame signal includes synchronizing bits, voice bits,
and control bits. The EX I/F 30 is therefore an analog telephone interface
(SLIC), an ISDN (Integrated Services Digital Network) basic interface EX
circuit (BRIS), an analog multifunction telephone interace circuit, a
digital multifunction telephone interface circuit (DLC) or similar
extension interface circuit customarily used with a PBX. The EX I/F 30 may
be implemented as a line package formed on a single circuit board. The
interface circuits accommodated in the line accommodating device 16 may,
of course, be interface trunks for connecting public telephone networks or
leased lines or ISPN primary rate interface trunks (BRIT).
More specifically, a plurality of KTSs 12 each are connected to the digital
EX I/F 30a by a pair of telephone wires 206. The EX I/F 30a feeds power to
the KTSs 12 and frames the PCM (Pulse Code Modulation) data of voice
signals received from the KTSs 12. The resulting frames are output to the
2MHW 32. Also, the EX I/F 30a disassembles frame signals input via the
2MHW 32 for reconstructing PCM signals and sends the PCM signals to the
KTSs 12. Such transfer is executed by a TCM (Time Compression Modulation)
system. The EX I/F 30a transforms compansion PCM coded voice signals
received from the KTSs 12 to frames and delivers them to the DP RAM 34 via
the 2MHW 32. If desired, the EX I/F 30a may be of the type including an
ISDN basic rate interface (BRI) to which ISDN terminals are connectable.
The EX I/F 30a executes conflict control over the KTSs 12 connected
thereto so as to allocate a particular time slot to each KTS 12 while
setting a particular address meant for each KTS 12.
As stated above, the digital EX I/F 30a connects the KTSs 12 and line unit
16 by performing the interchange of digital signals, synchronization,
encoding and decoding, assembly and disassembly of frames, conflict
control, address setting, and power feed and thereby effects the time
division transmission of voice frames.
As shown in FIG. 4, the KTSs 12 connected to the EX I/F 30a each include a
modular connector 400 to which the two-wire telephone line 206 is
connected. The modular connector 400 is connected to a multifunction CODEC
404 by a connection line 206 via an interface circuit not shown. The
multifunction CODEC 404 is connected to a bus 412 and a speech circuit
414. Also connected to the bus 412 are a CPU (Central Processing Unit)
406, keys 408 including numeral keys, and a display 410 including LEDs and
an LCD. The CODEC 404 decodes encoded data appearing on the connection
line 402 and delivers the decoded data to the speech circuit 414. Also,
the CODEC 404 encodes voice data output from the speech circuit 414 to PCM
codes and sends the PCM codes via the modular connector 400. The CPU 406
controls the various sections of the KTS 12 and distributes a signal to be
sent and a received signal to an encoder and a decoder, respectively,
constituting the CODEC 404. In addition, the CPU 406 inserts the
destination of a call and control information in a frame signal.
On the other hand, a plurality TELs 14 each are connected to a particular
analog EX I/F 30b by a pair of telephone wires 208. The EX I/F 30b
includes a plurality of extension interfaces adaptive to standard
telephones connected to a public telephone network. The EX I/F 30b has
various functions including the function of sending a calling signal, the
function of feeding currents for conversation, and the function of
monitoring DC. Specifically, the EX I/F 30b includes a CODEC and a
multiplexer/demultiplexer (MUX) although not shown specifically. The CODEC
encodes voice signals to output PCM data or decodes PCM data to output
voice signals. The multiplexer/demultiplexer multiplexes a plurality of
PCM data received from the TELs 14 by TDM and outputs the multiplexed PCM
data to the 2MHW 32 or demultiplexes frame signals input via the 2MHW 32
to thereby separate PCM data. The TELs 14 connected to the EX I/F 30b each
are connectable to a public analog telephone network although not shown
specifically.
The EX I/Fs 30a and 30b each are connected to the corresponding DP RAM 34
by the associated 2MHW 32. A protocol controller 60 controls the frame
signal input/output timings of the EX I/Fs 30a and 30b. The DP RAM 34 is a
transmit/receive buffer for temporarily storing 2 Mbps data including
voice and control frames and selectively transferring them to the
associated EX I/F 30a or 30b or to the associated packet processing
circuit 38.
Each packet processing circuit 38 is connected to the protocol controller
60, LAN I/F circuit 52 and the other packet processing circuits 38 by a
control bus 62. The packet processing circuit 38 provides voice packets
and a control packet with a LAN format and converts the packets and frame
signals on the 2MHW 32 to each other. FIG. 3 shows a specific
configuration of the packet processing circuit 38. As shown, the packet
processing circuit 38 is a packet assembling/disassembling circuit having
a VoIP (Voice over Internet Protocol) function for transmitting and
receiving packetized voice signals via an IP network and thereby effecting
telephone services. That is, the circuit 38 transforms frame signals at
the telephone side and the packets at the switching unit 18 side to each
other.
As shown in FIG. 3, the packet processing circuit 38 includes a bus I/F 302
connected to the bus 40 and a bus 300 arranged within the circuit 38.
Another bus I/F 304 is connected to the control bus 62 and bus 300. A CPU
or controller 306, CPU peripherals 308, a digital signal processor (DSP)
310 and a LAN controller (LANC) 312 are also connected to the bus 300. The
packet processing circuit 38 constitutes a computer system in which the
CPU 30 executes call processing, voice packet control and UDP/IP (User
Datagram Protocol/Internet Protocol) processing based on, e.g., ITU-T
recommendation H.323. A particular IP network address and a particular IP
host address on a computer network are assigned to each packet processing
circuit 38. The IP host address is made up of a destination IP address and
a source IP address. In the circuit 38, the IP addresses of the network
layer and UDP/IP addresses are added to packet headers. The LANC 312
transforms the packet headers with the above addresses to a LAN format and
then outputs them to the connection line 50. The packets 50, i.e., voice
and control packets generated by the circuit 38 under the synchronization
control of the protocol controller 60 are sent to the integrated
voice/data switching unit 18 via the LAN I/F 52, a connector (RJ45), and
the connection line 204. Further, the circuit 38 disassembles packets
appearing on the connection line 50 into frames. The CPU 306 and DSP 310
provides the frames with a 2MHW format and then outputs them to the 2MHW
or output 36.
Specifically, the DSP 310 performs encoding and decoding in accordance with
a voice encoding standard G.723.1 or G.729 and additionally performs
calculations for, e.g., tone signal generation. The DSP 310 encodes
generated signals including a tone signal and sends the resulting signals
to the EX I/F 30 via the DP RAM 34. The CPU peripherals 308 include a
clock generator, a memory, a memory controller, and an interrupt
controller.
The CPU or controller 306 controls voice and control packets, i.e.,
disassembles packets transferred from the network side via the connection
line 50 to thereby produce frames or assembles frame signals input from
the associated EX I/F 30 and DP RAM 34 via the 2MHW 36 into packets. The
CPU 306 performs the disassembly of packets and the assembly of frames
under the control of the protocol controller 60.
The LANC 312, which is an Ethernet 100/10BASE network interface, assembles
frames into packets defined on the LAN and delivers them to the connection
line 50 or disassembles packets into frames and delivers them to the bus
300. The LANC 312 adds its own hardware or physical address to a packet
header or determines whether or not a packet input via the connection line
50 is addressed to the associated unit by referencing a hardware address
added to the packet. The LANC 312 accepts only the packets addressed
thereto. The blocks 300 through 312 constituting the packet processing
circuit 38 may advantageously be mounted on a single semiconductor chip in
order to implement a VoIP processor LSI (Large Scale Integrated circuit).
Referring again to FIG. 1, the protocol controller 60 controls
synchronization between each packet processing circuit 38 and the EX I/F
30 associated therewith and terminals a protocol. Further, the protocol
controller 60 controls synchronization between each 2MHW 32 and the LAN,
i.e., controls the transmission/receipt control protocol of each line
package 30 connected to the packet processing circuit 38 by the connection
line 40, FIG. 3, and the protocol of the network as to timing.
The LAN I/F 52 is connected to the packet processing circuits 38 for
controlling both the processing circuits 38 and the connection line 204 of
the network as to the transmission and receipt of packets. In the
illustrative embodiment, the LAN I/F 52 includes a 100/10BASE LAN
interface and switches packets between the individual packet processing
circuit 38 and the integrated voice/data switching unit 18 connected
thereto by the connection line 204, FIG. 2.
As shown in FIG. 2, in the integrated voice/data switching unit 18
connected to the line unit 16 by the 100BASE network cable 204, the LAN-SW
20 interchanges voice and control packets with desired destinations. The
LAN-SW 20 gives priority to voice packets over control packets. The
switching unit 18 includes a 10BASE and a 100BASE LAN interface. Terminals
including the IP telephone 24 and server 22 and a computer terminal 64 are
connected to the 10BASE interface while the line accommodating device 16
is connected to the 100BASE interface.
The switching unit 18 connects and transfers each of voice packets and data
packets to a desired destination. In the illustrative embodiment, the
switching unit 18 switches voice packets and data packets while giving
priority to the former over the latter. The switching unit 18 controls the
connection of the packets to a host communication network and, e.g.,
telephones connected to each network. Further, the switching unit 18
executes the transfer of packets with the server 22 in accordance with,
e.g., an H.323 protocol.
FIG. 6 shows a specific configuration of the server 22. As shown, the
server 22 includes a connector (RJ45) and a LANC which are connected to
the integrated voice/data switching unit 18 by the network cable or
connection line 200. The server 22 constitutes a computer system with a
gateway function for allowing terminals inside and outside of the LAN to
communicate with each other. The server 22 includes a protocol conversion
600 for converting the protocol of the H.323 system and another protocol,
so that the server 22 can be connected to, e.g., a host public network.
Specifically, the protocol conversion 600 executes protocol conversion on
the basis of IP-packetized control data, i.e., a control packet so as to
control communication with a host communication network. The server 22 has
a band width control function, i.e., executes call control, address
resolution and priority control for voice packets 22 with the individual
telephone set and individual terminal accommodated in the voice/data
switching unit 18. In addition, the server 22 has a function of
registering applications including a telephone directory service and a
function of controlling a network.
FIG. 5 shows a specific configuration of the IP telephone 24 connected to
the integrated voice/data switching unit 18 by the network cable or
connection line 202. As shown, the IP telephone 24 is an Internet protocol
telephone including a VoIP processing circuit 500 in place of the CPU 406,
FIG. 4, of the KTS 12. The VoIP processing circuit 500 includes a
100/10BASE network interface. The circuit 500 is connected between the
network and the multifunction CODEC 404 and serves as a packet
assembler/disassembler for converting voice packets and PCM voice signals
to each other. The above network interface has an input 502 connected to a
connector (RJ45) which is connected to the network cable 202, and another
input 504 connected to a personal computer (PC) or similar terminal 26 via
a connector (RJ45).
An IP network address and an IP host address defined on the computer
network are also assigned to the VoIP processing circuit 500. The circuit
500 packetizes a PCM signal output from the CODEC 404, adds the IP address
to the resulting packet, adds an UDP/IP header to the same packet,
converts the packet with such headers to a LAN format, and delivers it to
the connection line 502. Further, the circuit 500 disassembles a packet to
separate a voice PCM signal and feeds the voice PCM signal to the CODEC
404. The CODEC 404 expands the input PCM signal.
Assume that the network computer or similar computer terminal 64 is
connected to the integrated voice/data switching unit 18 by the network
cable 202. Then, by installing software for implementing an Internet
telephone function in the computer terminal 64, it is possible to realize
a telephone function for effecting telephone conversation using IP
packets. This can be done with a microphone and a speaker connected to the
computer terminal 64. Even in such a case, conversation can be held
between the computer terminal 64 and a conventional analog telephone. As
for communication between personal computers, not only voices but also
video signals and numerical data can be packetized and interchanged.
The integrated voice/data switching system 10 having the above construction
will be operated as follows. Assume that one EX I/F 30a, for example,
included in the line unit 16 detects a call origination signal output from
one KTS 12 accommodated therein. Then, the EX I/F 30a packetizes call
origination information received from the KTS 12 and outputs the resulting
packet to the connection line 50 connected to the corresponding packet
processing circuit 38. The call origination information includes the
telephone number of the destination. The packet processing circuit 38
obtains an IP address and a port number corresponding to the telephone
number with, e.g., a gate keeper and generates a control packet meant for
the destination of the IP address. Call origination processing is executed
with the control packet.
During the above procedure, the DSP 310 included in the packet processing
circuit 30a generates a dial tone and a call tone at the consecutive
stages of call control, transforms them to PCM codes, and sends the PCM
codes to the EX I/F 30a via the 2MHW 36, DP RAM 34 and 2MHW 32. At the KTS
12, the CODEC 404 decodes the coded tone signals to thereby generate a
corresponding audible signal. This allows the operator of the KTS 12 to
input the telephone number of the destination and perform other desired
operations.
When the control packet generated by the packet processing circuit 38 is
input to the LAN-SW 20 of the integrated voice/data switching unit 18 via
the network cable 204, the LAN-SW 20 sends a call incoming report to the
telephone of the destination. If the telephone of the destination is the
IP telephone 24 at which the call can be terminated, the LAN-SW sends a
control packet including a ringing signal to the telephone 24. When the IP
telephone 24 is off-hooked, a conversation path is set up while, at the
same time, an answer packet is returned to the packet processing circuit
38 accommodating the calling KTS 12. When the EX I/F 30a is informed of
such a condition, it stops the call tone and allows voice frames to be
interchanged.
A PCM voice signal sent from the KTS 12 is converted to a voice frame
signal by the EX I/F 30a and then sent to the corresponding packet
processing circuit 38 via the 2MHWs 36 and 32 and DP RAM 34. The packet
processing circuit 38 generates an IP header on the basis of the input
frame, assembles a voice packet in accordance with the voice signal, and
sends the voice packet to the switching unit 18 via the connection line
50. On the other hand, when the packet processing circuit 38 detects a
voice packet meant for its own IP address via the connection line 50, it
disassembles the packet into voice frames and sends the resulting frame
signal to the EX I/F 30a via the 2MHWs 36 and 32 and DP RAM 34. The EX I/F
30a sends the frame signal to the KTS 12. The KTS 12 decodes the frame
signal and thereby outputs a voice signal. As for a call originated or
terminated at any one of the analog TELs 14, the EX I/F 30b accommodating
the TEL 14 executes PCM coding and decoding with voice signals.
If the called IP telephone 24 is busy, then the LAN-SW 20 returns a control
packet representative of the busy state to the corresponding packet
processing circuit 38. The packet processing circuit 38 transfers the
control packet to the EX I/F 30a accommodating the calling KTS 12. In
response, the EX I/F 30a generates a frame signal representative of the
busy state and sends it to the KTS 12.
Assume that a call is originated on the IP telephone 24. Then, when the
packet processing circuit 38 accommodating the destination of the call
detects a control packet sent from the IP telephone 24, it disassembles
the control packet, identifies the destination, and determines whether or
not the destination is busy. If the destination is not busy, the packet
processing circuit 38 sends a call incoming report to the corresponding EX
I/F 30. In response to the report, the EX I/F 30 causes the telephone at
the destination to ring. When the telephone at the destination is
off-hooked, the EX I/F 30 sets up a conversation path. This is also
followed by the previously stated processing for voice packet interchange.
As stated above, the line unit 16 connected to the integrated voice/data
switching system 10 can be implemented by existing extension/outside
interface circuits or similar line packages. The line unit 16 is connected
to the packet processing circuits 38 by time division communication path
(2MHW) interfaces and DP RAMs customary with a PBX. For example, an
interface circuit included in an existing PBX accommodates a plurality of
telephones or similar terminals while a plurality of units each having a
packet processing circuit, a DP RAM and an interface circuit are connected
by a LAN. The line unit 16 is connected to the switching unit 18 by the
connection line 50 and LAN I/F 52. It is therefore possible to easily
extend the configuration of the line unit 16 in order to increase or
decrease the number of lines to accommodate, as desired.
The line unit 16 allows, e.g., the existing analog TELs 14 to communicate
with the IP telephone set 24. Further, the line unit 16 allows the
telephones and personal computer or similar computer 64, FIG. 2, to
communicate with each other if a conversation program is installed in the
computer 64. Such conversation between different kinds of terminals is
applicable even to destination terminals not directly connected the
switching unit 18. For example, there can be effected conversation and
data interchange with terminals connected by an IP network and even
connection, if the device includes a trunk connected to a public network,
to destination telephones via an existing switching network.
When a conventional PBX system exists, it can be readily reconstructed into
a shared conversation/data switching system without newly installing
telephones, line packages or telephone wirings. That is, the switching
system 10 allows such existing devices to be accommodated in the line unit
16 and connected to the voice/data switching unit 18. This is successful
to use existing devices and therefore to smoothly reconstruct a
conventional telephone system using only voice signals into a shared
voice/data communication system. The device 16 may be built in the
switching unit 18 and does not have to be newly designed when use is made
of existing line packages. It follows that a switching system capable of
providing various kinds of services can be developed with a minimum number
of steps.
In summary, it will be seen that in accordance with the present invention,
there can be constructed a system capable of accommodating conventional
telephones and telephone wirings and even extension circuits and trunk
circuits associated with office lines, implementing voice communication
using a data communication network. This can be done without rearranging
the extension circuits, trunks or the like exclusively for the above
system and therefore with a minimum of designing and developing steps.
Further, the system allows, e.g., an analog telephone to communicate even
with a computer connected to a computer network or an IP telephone.
Particularly, a conventional voice communication switching system can be
readily reconstructed into a system capable of integrating voice
communication and data communication.
The entire disclosure of Japanese patent application No. 170401/1999 filed
Jun. 17, 1999 including the specification, claims, accompanying drawings
and abstract of the disclosure is incorporated herein by reference in its
entirely.
While the present invention has been described with reference to the
illustrative embodiment, it is not to be restricted by the embodiment. It
is to be appreciated that those skilled in the art can change or modify
the embodiment without departing from the scope and spirit of the present
invention.
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