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Claims  |
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We claim:
1. A method for use in an exchange system provided with first and second
information signals, and generating first and second control signals, said
exchange system including an attendant console and an attendant console
control circuit which are coupled together by a two-way transmission line
including a signalling channel and a plurality of information channels in
both an upstream frame and a downstream frame, the method comprising the
steps of:
a) multiplexing the first information signal and the first control signal
including at least one of a first display signal, a lamp signal and a
first incoming call ringing signal, from the attendant console control
circuit, to produce a first multiplexed signal, the first information
signal and the first control signal being multiplexed in first and second
information channels, respectively, the first and second information
channels each having respective bandwidths larger than a bandwidth of the
signalling channel;
b) transmitting the first multiplexed signal from the attendant console
control circuit to the attendant console on the downstream frame of the
two-way transmission line;
c) multiplexing the second information signal and the second control signal
including a key signal, to produce a second multiplexed signal, the second
information signal and the second control signal being multiplexed in
third and fourth voice information channels, respectively, the third and
fourth information channels each having respective bandwidths larger than
a bandwidth of the signalling channel; and
d) transmitting the second multiplexed signal from the attendant console to
the attendant console control circuit on the upstream frame of the two-way
transmission line.
2. A method for use in an exchange system which is provided with an
information signal, and which generates a control signal, said exchange
system including an attendant console and an attendant console control
circuit which are coupled together by a transmission line, the method
comprising the steps of:
a) multiplexing the information signal and the control signal including at
least one of a display signal, a lamp signal and an incoming call ringing
signal, to produce a multiplexed signal, the information signal and the
control signal being multiplexed in first and second integrated services
digital network (ISDN) standard B-channels, respectively, of the
multiplexed signal; and
b) transmitting the multiplexed signal from the attendant console control
circuit to the attendant console on the transmission line.
3. A method for use in an exchange system which is provided with an
information signal, and which generates a control signal, said system
including an attendant console and an attendant console control circuit
which are coupled together by a transmission line including a plurality of
B-channels, the method comprising the steps of:
a) multiplexing the information signal and the control signal including a
key signal, to produce a multiplexed signal, the information signal and
the control signal being multiplexed in first and second B-channels,
respectively, of the multiplexed signal; and
b) transmitting the multiplexed signal from the attendant console to the
attendant console control circuit on the transmission line.
4. A system supplied with first and second information signals and
generating first and second control signals, said exchange system
including an attendant console and an attendant console control circuit
which are coupled together by a two-way transmission line, including a
signalling channel and a plurality of information channels in both an
upstream frame and a downstream frame, said system comprising:
the attendant console control circuit for multiplexing the first
information signal and the first control signal, including at least one of
a display signal, a lamp signal, and an incoming call ringing signal, in
first and second information channels, respectively, and demultiplexing
the second multiplexed signal into the second information signal and the
second control signal; and
the attendant console, coupled to the attendant console control circuit,
for multiplexing the second information signal and the second control
signal including a key signal, into first and second information channels,
respectively, and demultiplexing the first multiplexed signal into the
first control signal and the first information signal, the attendant
console being responsive to the first control signal,
the attendant console control circuit transmitting the first multiplexed
signal to the attendant console on the downstream frame of the
transmission line, and
the attendant console transmitting the second multiplexed signal to the
attendant console control circuit on the upstream frame of the
transmission line.
5. A system as claimed in claim 4, wherein the system is coupled to a
telephone line for a public telephone network, the telephone line
transmitting an incoming call including an incoming call ringing signal,
from a calling party, further comprising:
a switch circuit operatively coupled to receive the incoming call; and
a central control circuit operatively coupled to the switch circuit and the
attendant console control circuit, to receive the incoming call ringing
signal to transmit as the first control signal to the attendant console
control circuit in a first time period, to control the switch circuit to
switch the incoming call to the attendant console control circuit as the
first speech signal in a second time period, based on the second control
signal received from the attendant console control circuit in a third time
period, and to control the switch to transmit the second speech signal to
the telephone line in a fourth time period.
6. A system as claimed in claim 4, further comprising:
a central control circuit to generate the first control signal including at
least one of the display signal and the lamp signal, based on the second
control signal.
7. A system as claimed in claim 4, further comprising:
a transmission line coupled between the attendant console control circuit
and the attendant console, for carrying the first and second multiplexed
signals transmitted by the attendant console control circuit and the
attendant console, respectively.
8. A system as claimed in claim 4,
wherein the first control signal is received in a first time period by the
attendant console which activates a lamp in the attendant console, based
on the incoming call ringing signal,
wherein an attendant console operator responds to the incoming call ringing
signal to receive the first speech signal, in a second time period,
wherein the attendant console operator determines an extension
corresponding to a called party from a calling party generating the first
speech signal, the extension being coupled to a switch,
wherein the attendant console operator operates a key to generate a key
signal transmitted as the second control signal in a third time period,
and
wherein a central control circuit coupled to the switch and the attendant
console control circuit, controls the switch to transmit the first speech
signal to the extension in a fourth time period, based on the second
control signal.
9. An exchange system provided with an information signal and generating a
control signal, said exchange system including an attendant console and an
attendant console circuit coupled together by a transmission line, said
exchange system comprising:
a multiplexer for receiving the information signal and the control signal,
for multiplexing the information signal and the control including at least
one of a display signal, a lamp signal and an incoming call ringing
signal, to produce a multiplexed signal;
first and second integrated service digital network (ISDN) standard
B-channels for multiplexing the information signal and the control signal,
respectively, of the multiplexed signal; and
a transmitter for transmitting the multiplexed signal from the attendant
console circuit to the attendant console in the transmission line.
10. An exchange system provided with an information signal and generating a
control signal, said exchange system including an attendant console and an
attendant console control circuit coupled together by a transmission line
and including a plurality of B-channels, said exchange system comprising:
a multiplexer for receiving the information signal and the control signal
including a key signal, for producing a multiplexed signal;
first and second B-channels, connected to receive the information signal
and the control signal, for multiplexing the information signal and the
control signal, respectively, of the multiplexed signal; and
a transmitter, connected to secure the multiplexed signal, for transmitting
the multiplexed signal from the attendant console to the attendant console
circuit on the transmission line. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a private branch exchange system having
connected thereto an attendant console and a plurality of extensions.
In private branch exchange systems, an attendant console is connected
thereto for responding to an incoming call from a telephone line which is
connected with a public telephone network, and calling a party on an
extension to which a calling party requests to speak. Conventionally, in
middle or large-size private branch exchange systems, a plurality of
attendant consoles are provided in an attendant console room which is
located near the main frame of the private branch exchange system.
However, recently, in many factories and offices, the plurality of
attendant consoles are located dispersively, for example, in reception
offices and secretaries' offices in a plurality of divisions or
departments. Generally, a large number of control signals are required to
be transmitted between the main frame of the private branch exchange
system and the attendant console through long distances.
(2) Description of the Related Art
FIG. 1 shows a construction of a conventional private branch exchange
system. In FIG. 1, reference numeral 30 denotes a public telephone line,
40 denotes the main frame of the private branch exchange system, 41
denotes a trunk circuit connecting with the public telephone line, 42
denotes a switch circuit, 431 and 432 each denote an attendant console
control circuit, 44 denotes a central control circuit, 441 and 442 each
denote an attendant console, 461 and 462 each denote a set of transmission
lines connected between an attendant console and the main frame of the
private branch exchange system, 451 and 453 each denote a lamp indicating
portion, 452 and 454 each denote a key input portion, and 50 denotes an
extension.
In the construction of FIG. 1, when a call is incoming in the trunk circuit
41, the central control circuit 44 sends a control signal which indicates
that a call is incoming to all the attendant consoles 441 and 442 through
the corresponding attendant console control circuits 431 and 432.
Responding to the signal, lamp indicators in the lamp indicating portions
451 and 453 which indicate an incoming call from the public telephone line
30, are turned on in each of the attendant consoles 441 and 442. When an
operator at one of the attendant consoles 441 and 442 pushes a key the
input from which generates a control signal which indicates that the
operator at the attendant console will respond to the incoming call, the
control signal from the attendant console is transmitted to the central
control circuit 44 through the corresponding attendant console control
circuit. Responding to the control signal which is first received in the
central control circuit 44, the central control circuit 44 controls the
switch circuit 42 to connect the above attendant console control circuit
431 from which the above control signal has been first sent to the central
control circuit 44, to the trunk circuit 41. Thus, the operator at the
attendant console 441 can speak with the calling party through the
attendant console control circuit 431 and the trunk circuit 41, and can
learn the party to which the calling party wishes to speak, by speaking
with the calling party. When the operator at the attendant console 431
recognizes the party to which the calling party wishes to speak, the
operator inputs the number of the extension of the party to which the
calling party wishes to speak, from the key input portion 452. The number
of the extension is transmitted from the attendant console 441 to the
attendant console control circuit 431, and is transferred to the central
control circuit 44. Receiving the number of the extension of the party to
which the calling party wishes to speak, the central control circuit 44
controls the switch circuit 42 to connect the extension of the party to
which the calling party wishes to speak, to the trunk circuit 41.
In the above operation, the man-machine interface at the attendant consoles
441 and 442 is realized by the keys in the key input portions 452 and 454
and the lamp indicators in the lamp indicating portions 451 and 453. The
lamp indicators turn on and off responding to pushing of the keys, and it
is required that the delay of the turn-on or turn-off of the lamp
indicators in the response to the pushing of the keys is less than 200
msec so as to be natural to the operator.
In the prior art, the CCITT V.11 system is utilized for transmission of
control signals between attendant console control circuits and
corresponding attendant consoles. According to the CCITT V.11
recommendation, a balanced cable is used for transmission of control
signals in each direction from an attendant console control circuit to a
corresponding attendant console, and from the attendant console to the
corresponding attendant console control circuit, i.e., a pair of balanced
cables are laid between each of the attendant consoles 441 and 442 and the
main frame 40 of the private branch exchange system, in addition to
transmission lines for transmitting speech signals between each of the
attendant consoles 441 and 442 and the main frame 40 of the private branch
exchange system. As mentioned before, recently, the attendant consoles are
located dispersively around the main frame of the private branch exchange
system, and therefore, the distances between the attendant consoles and
the main frame 40 of the private branch exchange system are large.
However, generally, the above V11 system requires additional equipment for
a long distance transmission, and the provision of the additional
equipment increases cost for construction. Further, when the distances
between the attendant consoles and the main frame 40 of the private branch
exchange system are large, the cost in constructing the whole private
branch exchange system is increased due to the above laying of the pair of
balanced cables.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a private branch exchange
system having connected thereto an attendant console and a plurality of
extensions, wherein transmission between a main frame of the system and
the attendant consoles can be carried out using a small number of
transmission lines, and thereby the cost for constructing the whole system
is reduced.
According to the present invention, there is provided a private branch
exchange system connecting a telephone line of a public telephone network
and a plurality of extensions thereto, comprising a main frame, at least
one attendant console, and a transmission line, provided for each
attendant console. The main frame comprises a trunk circuit, a switch
circuit, a central control circuit, and at least one attendant console
control circuit. Each of the above attendant console responds to an
incoming call, receives a speech signal from a calling party, sends a
speech signal to the calling party, inputs control information for
transferring an incoming call to one of the plurality of extensions, sends
control signals to the central control circuit, and receives control
signals from the central control circuit. Each of the transmission line
connects the attendant console with the corresponding attendant console
control circuit and, transmits the control signals between the attendant
console with the corresponding attendant console control circuit. The
trunk circuit is connected to the telephone line of the public telephone
network. The trunk circuit receives an incoming call through the public
telephone network, and transmits an incoming and outgoing speech signal.
The switch circuit connects the trunk circuit with one of the attendant
console and the plurality of extensions under control of the central
control circuit. The central control circuit sends control signals to the
attendant console and receives control signals from the attendant console,
and controls the switch circuit to connect the trunk circuit with one of
the attendant consoles and the plurality of extensions according to the
control signal from one of the attendant consoles. Each of the attendant
console control circuits comprises a first multiplex transmission circuit
which multiplexes the speech signal from the switch circuit and the
control signals from the central control circuit, and transmits the
multiplexed signal on the transmission line. The first multiplex
transmission circuit further receives a signal from the transmission line,
and demultiplexes the received signal into a speech signal which is to be
sent to the switch circuit, and control signals which are to be sent to
the central control circuit. The attendant console further comprises a
second multiplex transmission circuit which multiplexes the speech signal
from the switch circuit and the control signals from the central control
circuit, and transmits the multiplexed signal on the transmission line,
and the second multiplex transmission circuit further receives a signal
from the transmission line, and demultiplexes the received signal into a
speech signal and control signals.
Further, the above first and second multiplex transmission circuits
alternately and periodically send and receive the multiplexed signal
through the transmission line.
Alternatively, the first and second multiplex transmission circuits send
and receive the multiplexed signals through the transmission line so that
the multiplexed signals from the first and second multiplex transmission
circuits are transmitted simultaneously on the transmission line as a
frequency division multiplex transmission.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of the conventional private branch exchange
system having connected thereto an attendant console and a plurality of
extensions;
FIGS. 2A and 2B are block diagrams of a private branch exchange system
having connected thereto an attendant console and a plurality of
extensions, in an embodiment of the present invention; and
FIG. 3 shows the data format and timing in the transmission between an
attendant console control circuit in the main frame of the private branch
exchange system and an attendant console in the construction of FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 2 is a block diagram of a private branch exchange system having
connected thereto an attendant console and a plurality of extensions, in
an embodiment of the present invention. Only the construction including an
attendant console and a corresponding attendant console control circuit,
is shown in FIG. 2, and the construction of the private branch exchange
system in the embodiment of the present invention which is not shown in
FIG. 2, is the same as the construction of FIG. 1. In FIG. 2, reference
numeral 10 denotes the main frame of the private branch exchange system,
22 denotes a switch circuit, 21 denotes an attendant console control
circuit, 23 denotes a central control circuit, 25 denotes an attendant
console and, 24 denotes a two-wire transmission line connected between the
attendant console 25 and the main frame 10 of the private branch exchange
system. Numerals 211 and 251 each denote a time compression multiplex
transmission control circuit, 212 and 253 each denote an asynchronous
transmission control circuit, 252 denotes a speech signal transformation
circuit, 254 denotes a lamp indication control circuit, 255 denotes a key
input control circuit, 214 and 256 each denote a microprocessor unit, 213
and 257 each denote a memory, and 258 denotes a headset comprising a
microphone and an ear receiver.
In the construction of FIG. 2, the central control circuit 23 holds all the
statuses of the private branch exchange system, sends control signals of
the statuses to the attendant console control circuits (including the
attendant console control circuit 21), receives control signals which are
generated by key operations at the attendant consoles (including the
attendant console 25), and controls the switch circuit 22 to connect the
trunk circuit with one of the attendant console control circuits or
extensions according to an incoming call or the control signals from the
attendant consoles. When the microprocessor unit 214 in the attendant
console control circuit 21 receives a control signal from the central
control circuit 23 through the interface circuit 215, the microprocessor
unit 214 stores the status which is indicated by the received control
signal in a corresponding address in the memory 213. The memory 213 in the
attendant console control circuit 21 holds the statuses of the private
branch exchange system which are necessary for the corresponding attendant
console 25.
The statuses held in the memory 213 are periodically sent to the
corresponding attendant console 25 through the asynchronous transmission
control circuit 212, the time compression multiplex transmission control
circuit 211, and the two-wire transmission line 24. Each byte of the above
statuses held in the memory 213 is read and is sent to the asynchronous
transmission control circuit 212 as control signals in the form of
parallel data under control of the microprocessor unit 214. The
asynchronous transmission control circuit 212 transforms the received
parallel data comprised of each eight bit portion of the above statuses,
into a serial form, and sends the serial data as control signals to the
time compression multiplex transmission control circuit 211 as an
asynchronous transmission, for example, a start-stop transmission.
The time compression multiplex transmission control circuits 211 and 251
are provided for controlling the transmission of the control signals
between the attendant console control circuit 21 and the attendant console
25 through the two-wire transmission line 24. FIG. 3 shows the data format
and timing in the transmission between the attendant console control
circuit 21 in the main frame 10 of the private branch exchange system and
an attendant console 25 in the construction of FIG. 2. As shown in FIG. 3,
the transmission between the attendant console control circuit 21 and the
attendant console 25 is carried out periodically in the period of T=125
.mu.sec. Transmission of a downstream frame from the attendant console
control circuit 21 to the attendant console 25 is carried out in the first
half cycle of each cycle T in a burst mode, and transmission of an
upstream frame from the attendant console 25 to the attendant console
control circuit 21 is carried out in the second half cycle of each cycle T
in a burst mode. In each of the downstream frames and the upstream frames,
"F" denotes a frame synchronization pattern, "B1" denotes a B1 channel,
"B2" denotes a B2 channel, and "D" denotes a D channel, i.e., each
transmission frame contains three channels. Each of the B1 and B2 channels
contains 8 bits, and the D channels contains 2 bits. Namely, the
transmission rate of each of the B1 and B2 channels is 64 Kbps, and the
transmission rate of the D channel is 16 Kbps.
The time compression multiplex transmission control circuit 211 in the
attendant console control circuit 21 receives digital speech signal (PCM
signal) which has been transmitted from the calling party through the
telephone line, the trunk circuit, and the switch circuit 22, and the
above control signals from the asynchronous transmission control circuit
212, multiplexes the received signals in the frame as shown in FIG. 3, and
sends them through the two-wire transmission line 24 to the corresponding
attendant console 25, in the above first half cycle. The time compression
multiplex transmission control circuit 211 receives the multiplexed signal
in the frames as shown in FIG. 3 through the two-wire transmission line 24
from the corresponding attendant console 25, demultiplexes the received
signal into the digital speech signal (PCM signal) and the above control
signals, and sends the digital speech signal (PCM signal) to the switch
circuit 22, and the control signals to the asynchronous transmission
control circuit 212, in the above second half cycle. The digital speech
signal is transmitted to the calling party through the switch circuit 22,
the trunk circuit, and the telephone line. The above digital speech
signals are transmitted through the B1 channel, and the above control
signals are transmitted through the B2 channel. The D channel is not used.
The asynchronous transmission control circuit 212 transforms the control
signals which are received from the time compression multiplex
transmission control circuit 211 into parallel one-byte data, and
transfers the parallel data (control signals) to the microprocessor unit
214. When the microprocessor unit 214 receives the control signals from
the asynchronous transmission control circuit 212, the received control
signals are once stored in the memory 213 as a part of the statuses, and
are then transferred to the central control circuit 23 through the
interface circuit 215.
In the attendant console 25, the time compression multiplex transmission
control circuit 251 functions in a similar manner to the above time
compression multiplex transmission control circuit 211. The time
compression multiplex transmission control circuit 251 receives the above
multiplexed signal in the frame as shown in FIG. 3 through the two-wire
transmission line 24 from the corresponding attendant console 25,
demultiplexes the received signal into the digital speech signal (PCM
signal) and the above control signals, and sends the digital speech signal
(PCM signal) to the speech signal transformation circuit 252, and the
control signals to the asynchronous transmission control circuit 253, in
the above first half cycle.
The speech transformation circuit 252 receives the digital speech signal
from the time compression multiplex transmission control circuit 251, and
transforms the received digital speech signal into an analog speech
signal. The analog speech signal is supplied to the ear receiver in the
headset 258. An analog speech signal which is generated in the microphone
in the headset is input into the speech signal transformation circuit 252,
and is transformed to a digital speech signal to be supplied to the time
compression multiplex transmission control circuit 251.
The key input control circuit 255 is provided for generating a key input
signal responding to a key operation by an operator. The key input signal
is once stored in the memory 257 under control of the microprocessor unit
256 as control information, and the control information which is held in
the memory 257 is then transferred to the asynchronous transmission
control circuit 253 as control signals under control of the microprocessor
unit 256 in a parallel form. When the asynchronous transmission control
circuit 253 receives the parallel control signals from the memory 257, the
asynchronous transmission control circuit 253 transforms the parallel
control signals into a serial form, and the control signals in the serial
form are transferred to the time compression multiplex transmission
control circuit 251.
The time compression multiplex transmission control circuit 251 receives
the above digital speech signal from the speech signal transformation
circuit 252, and the control signals from the asynchronous transmission
control circuit 253, multiplexes the received signals in the frame as
shown in FIG. 3, and sends the multiplexed signals through the two-wire
transmission line 24 to the corresponding attendant console control
circuit 21, in the above second half cycle.
When the asynchronous transmission control circuit 253 receives the above
control signals from the time compression multiplex transmission control
circuit 253 in a serial form, the control signals are transformed into a
parallel form, and are then transferred to the memory 257 as statuses and
to the microprocessor unit 256 as an asynchronous transmission. The
microprocessor unit 256 stores the received control signals in the memory
257, and controls the lamp indication control circuit 254 to turn on the
light indicators according to the statuses which are held in the memory
257.
In the above construction, the control signals which are transmitted from
the central control circuit 23 to the attendant console 25 include, for
example, a status signal indicating that a call is incoming, and the
control signals which are transmitted from the attendant console 25 to the
central control circuit 23, include, for example, dialing information
which has been input from the key input portion of the attendant console
25 by the operator, and is transmitted from the attendant console 25 to
indicate a number of an extension of a party to which a calling party
wishes to speak. All control signals are repeatedly transmitted between
the attendant console control circuit 21 and the attendant | | |
