Electronic exchange and key telephone system

Details Electronic exchange and key telephone system Electronic exchange and key telephone system

2000-08-22

2004-02-03

Chiang, Jack (Department: 2642)

Telephonic communications

Special services

Call diversion

C379S212010, C379S088120

Reexamination Certificate

active

06687361

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-235008, filed Aug. 23, 1999; and No. 2000-246319, filed Aug. 15, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to an electronic exchange and a key telephone system.
An electronic exchange has been capable of controlling call reception from and call transmission to other electronic exchanges by employing the QSIG protocol defined by the European Computer Manufacturers Association, which is the international standard for digital lines.
The services can be provided by constructing the networking by use of this kind of electronic exchanges as if one single electronic exchange were operated for the user using the electronic exchanges.
FIG. 1
is a view showing a networking using conventional electronic exchanges.
FIG. 2
is a view showing a sequence of a message signal forwarded between the electronic exchanges in the networking of FIG.
1
.
In
FIG. 1
electronic exchanges
10
,
11
and
12
are respectively connected to one another in digital lines
21
,
22
and
23
employing the QSIG protocol.
It is assumed now that telephones
1
and
2
communicate with one another via the electronic exchanges
10
and
11
, and the telephone
2
forwards the call with the telephone
1
to a telephone
3
connected to the electronic exchange
12
so that the telephones
1
and
3
communicate with one another.
When the user of the telephone
2
executes hooking operation to the electronic exchange
11
, a dial tone signal is transmitted from the electronic exchange
11
to the telephone
2
. At the same time, the telephone
1
of the communication partner is made to be in the on-hold state by the electronic exchange
11
.
The user of the telephone
2
dials a telephone number of the telephone
3
as the forwarding destination by the telephone
2
after having confirmed the dial tone.
The electronic exchange
11
transmits a forward acknowledgement signal “Facility message” defined by the QSIG protocol to a digital line
22
, in response to the dialing. At this time, specific information about the telephone number of the call destination, a person who forwards this message, a person who receives the forwarded message, etc., i.e. facility information elements are added to the Facility message.
Receiving the “Facility message” from the electronic exchange
11
, the electronic exchange
12
checks whether the telephone
3
is idle or not. If the telephone
3
is idle, the electronic exchange
12
transmits to the electronic exchange
11
a “Call proceeding message”, which indicates that the forwarding is acceptable.
On the other hand, the telephone
2
is in the on-hook state and remains idle after the dialing.
Receiving the “Call proceeding message” from the electronic exchange
12
, the electronic exchange
11
recognizes that the telephone
3
, which is a destination of a call to be forwarded to the electronic exchange
10
, is idle and can accept the call. At this time, the electronic exchange
11
inserts the information about the forwarding into the “Facility message” and transmits the message to the electronic exchange
10
so that the electronic exchange transmits a calling request “Setup message” as a formal call start request to the electronic exchange
12
.
The electronic exchange
10
transmits the “Setup message” to the electronic exchange
12
in accordance with the information included in the “Facility message”.
Receiving the “Setup message”, the electronic exchange
12
checks again whether the telephone
3
is idle or not. If the telephone
3
is idle, the electronic exchange
12
transmits the “Call proceeding message”, which represents the acknowledgement of acceptance for the call, to the electronic exchange
10
. At the same time, the electronic exchange
12
transmits a calling signal to the telephone
3
and transmits “Alerting”, which represents a state of extension calling, to electronic exchange
10
.
Incidentally, with the conventional electric exchanges, in a case where a calling operation is executed at the telephone
3
or a call from the other telephones is received at the telephone
3
after the electronic exchange
12
has received the “Facility message” and transmitted the “Call proceeding message” representing that the forwarding is acceptable, when there is an incoming call from the electronic exchange
10
, the telephone
3
is busy and thus the forwarding is not accomplished, as shown in a flow chart of FIG.
3
. In this case, there is also a drawback that the data traffic unnecessarily increases since an invalid signal is transmitted within the network.
Calling restriction as to whether a call from extension telephones should be accepted is often executed in accordance with international, longdistance and local destinations of calling. In this case, with the conventional electronic exchanges, the information unique to the manufacturer, common to only electronic exchanges of the same manufacturer is inserted into the manufacturer information element of the QSIG protocol, and is provided to electronic exchanges connected to the public telephone network by those connected to extension telephones.
Transmission of the manufacturer information element needs to be executed under the dedicated coding rules, and software for transmission and reception is also required. For this reason, the load on the CPU (central processing unit) in the electronic exchange may increase, technical problems may arise, and circuitry may be complicated due to the addition of new hardware.
FIG. 4
is a block diagram showing a configuration of a conventional key telephone system adapted to U point of an ISDN line.
A key telephone system
50
includes an ISDN interface unit (I/F unit)
51
for connecting with an ISDN network
60
and an ISDN terminal
70
, and a control unit
52
for controlling the ISDN interface unit
51
and executing the calling process and the speech exchange process.
The ISDN interface unit
51
and the control unit
52
exchange various signals such as speech data, a clock signal, a frame synchronization signal, a control signal, etc. via an internal bus
53
.
FIG. 5
is a block diagram showing the structures of the ISDN interface unit
51
and the control unit
52
.
The ISDN interface unit
51
includes an interface LSI
80
for interfacing (called NT) with the ISDN network
60
, and an interface LSI
81
for interfacing (called LT) with the ISDN terminal
70
. The interface LSI
80
is fixed to the NT mode that allows the operation to be made in accordance with a clock signal extracted from the ISDN network
60
. The interface LSI
81
is fixed to the LT mode that makes the terminal synchronous by using its own clock signal. A port corresponding to the NT mode is called a line port and a port corresponding to the LT mode is called an extension port.
When the interface LSI
80
is set to extract clock signal CLK from the ISDN network
60
, i.e. when the interface LSI
80
is set in the NT mode, a switch unit
82
is turned on and a switch unit
84
is turned off. The interface LSI
80
extracts the clock signal CLK from the ISDN network
60
and outputs the signal through its own clock port.
The clock signal CLK that is output from the interface LSI
80
is input to a timing generation unit
85
of the control unit
52
as basic clock signal CLKb through the switch unit
82
.
The timing generation unit
85
generates system clock signal CLKs in accordance with the basic clock signal CLKb and supplies this signal to both a time switch unit
86
of the control unit
52
and a phase adjustment time switch unit
83
of the ISDN interface unit
51
to make synchronization in the system. The timing generation unit
85
also generates a frame synchronization signal FS and outputs the signal to the phase adjustment time switch unit
83
and the time switch unit
86
.
Synchronization between the interface LSI
80
and the interface

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