Store and forward switching type communication control apparatus

A store and forward switching type communication control apparatus for use in a facsimile communication system includes a switching unit, a plurality of internal line interfaces, a plurality of external line interfaces, a plurality of facsimile communication units, a tone generator, a memory and a control unit. The internal line interfaces are connected to a plurality of terminal units, such as telephone units and facsimile units, through respective internal lines. The external line interfaces are connected to an external communication network, such as a telephone network. When one of the terminal units is off-hooked, the availability status of the resources, such as the external line interfaces, the facsimile communication units and the memory, which are available to that terminal unit which has been off-hooked is examined and its result of examination is supplied to the terminal unit in question in order to apprise the operator of the current availability status of the resources.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention generally relates to a dual mode communication control 
apparatus having both of a direct communication mode and a store and 
forward communication mode, and, in particular, to a store and forward 
switching type communication control apparatus connected between a 
plurality of internal and external lines. 
2. Description of the Prior Art 
A store and forward switching type communication apparatus capable of once 
storing image information to be transmitted in a memory and then 
transmitting the thus stored image information to a destination station 
has recently attracted attention due to the recent rapid dissemination of 
facsimile machines. Such a store and forward switching type communication 
apparatus has two modes of operation, i.e., (1) a direct communication 
mode, in which one of the internal lines is directly connected to one of 
the external lines to carry out communication in response to a call 
received through either an internal or external line and (2) a store and 
forward communication mode, in which, when a call has been received from 
one of the internal lines, the image information transmitted through this 
internal line is once stored in a memory, and then the thus stored image 
information is transmitted to a destination station at a designated time. 
In the direct communication mode, the store and forward switching type 
communication control apparatus carries out a sequence of operation, 
including the steps of (1) off-hook from a telephone unit or a facsimile 
machine connected to one of the internal lines; (2) apprising of the 
off-hook status to a control unit through an interface of the internal 
line; (3) securing of resources of the internal line interface by the 
control unit; (4) designating a connection between the internal line 
interface and a DT (dial tone) sound source from the control unit to a 
switching unit; (5) inputting (designation of operation and the telephone 
number of the destination station) by dialing (dial pulse signal (DP) or 
push button signal (PB)) from the internal line side; (6) designating a 
release of connection between the internal line interface and the DT sound 
source from the control unit to the switching unit; (7) securing of an 
external line interface; (8) instructing the external interface to place a 
call to the destination station; (9) designating a connection between the 
internal interface and the external interface from the control unit to the 
switching unit; (10) initiation of facsimile communication (or aural 
communication); (11) off-hook from the internal line side; (12) apprising 
of the off-hook status to the control unit from the internal interface; 
and (13) releasing of the resources (disconnecting the switching unit from 
the internal and external interfaces). 
On the other hand, during the store and forward communication mode, the 
store and forward communication apparatus carries out a sequence of steps, 
which include: (1) off-hook signal from a telephone unit or facsimile 
machine connected to an internal line; (2) apprising of the off-hook 
status to the control unit from the internal line interface; (3) securing 
of resources of the internal line interface by the control unit; (4) 
designating a connection between the internal line interface and a DT 
sound source from the control unit to the switching unit; (5) inputting 
(designation of operation and the telephone number of the destination 
station) by dialing (DP or PB) from the internal line side; (6) 
instructing the switching unit to release a connection between the 
internal line interface and the DT sound source from the control unit; (7) 
apprising a store and forward communication operation and the telephone 
number of the destination station to the control unit from the internal 
line interface; (8) designating a connection between the internal line 
interface and a communicating means for facsimile communication from the 
control unit to the switching unit; (9) instructing a reception operation 
to the communicating means for facsimile communication from the control 
unit; (10) designating transmission to a facsimile machine connected to 
the internal line; (11) initiation of facsimile communication; (12) 
storing of received image information into storing means from the 
communicating means for facsimile communication; (13) completion of 
facsimile communication; (14) off-hook signal from the internal line; (15) 
apprising of off-hook from the internal line interface to the control 
unit; and (16) releasing of the resources (disconnection among the 
internal line interface, the communication means for facsimile 
communication and the switching unit). 
With this structure, since a plurality of communication terminals, such as 
telephone units and/or facsimile machines, can be managed by a common 
store and forward switching communication control apparatus, the use rate 
of a transmission network can be significantly enhanced. However, in such 
a prior art store and forward switching type communication control 
apparatus, when transmission is to be carried out from an internal line to 
an external line, it is only after inputting of operational instructions 
and the telephone number of a destination station by an operator of a 
communication terminal connected to the internal line that the status of 
various resources of the communication control apparatus, such as 
interfaces, transmission lines, communicating means and storing means, is 
checked and securing of resources is carried out. Thus, there is a case in 
which, even if a dial tone is properly generated during off-hook, required 
resources cannot be secured by a dialing operation because such resources 
as interfaces and transmission lines are in the busy status, thereby 
waisting the operation by the operator. In this case, the exactly the same 
operation must be repeated by the operator and thus there is a lack of 
easiness or convenience in operation. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided a store and 
forward switching type communication control apparatus in which, when an 
off-hook signal is supplied from a terminal unit through an internal line, 
the status of resources available to that internal line is first examined 
and the result of the examination is supplied to the terminal unit through 
the internal line. With this structure, since the current status of 
available resources is supplied to an operator at the terminal unit before 
the operator executes a required input operation, such as inputting of 
operational commands and the telephone number of a destination station, to 
the terminal unit, the operator is not required to execute the same input 
operation repetitively as in the prior art. 
It is therefore a primary object of the present invention to obviate the 
disadvantages of the prior art as described above and to provide an 
improved store and forward switching type communication control apparatus. 
Another object of the present invention is to provide an improved store and 
forward switching type communication control apparatus high in efficiency 
and operability. 
A further object of the present invention is to provide an improved store 
and forward switching type communication control apparatus capable of 
preventing an operator's operation from being nullified because of the 
lack of availability of a required resource. 
Other objects, advantages and novel features of the present invention will 
become apparent from the following detailed description of the invention 
when considered in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIG. 1, there is schematically shown in block form a 
facsimile communication system 1 using a store and forward switching type 
communication control apparatus constructed in accordance with one 
embodiment of the present invention. As shown, the facsimile communication 
system 1 includes a store and forward switching type communication control 
apparatus 2, a plurality of internal lines LI.sub.1 through LI.sub.n 
connected to the communication control apparatus 2, a plurality of 
external lines LO.sub.1 through LO.sub.m connected to the communication 
control apparatus 2, and a plurality of facsimile terminal units FI.sub.1 
through FI.sub.n connected to the plurality of internal lines LI.sub.1 
through LI.sub.n, respectively. The plurality of external lines LO.sub.1 
through LO.sub.m have their opposite ends connected to a transmission 
network, such as a telephone network 3. 
As shown in FIG. 2, the store and forward switching type communication 
control apparatus 2 includes a switching unit 21, a plurality of external 
line interfaces A.sup..multidot. I/F.sub.1 through A.sup..multidot. 
I/F.sub.m, a plurality of facsimile communication units (communication 
means) F.sub.1 through F.sub.x, internal line interfaces B.sup..multidot. 
I/F.sub.1 through B.sup..multidot. I/F.sub.n, a tone generator 22, an 
interface 23, a memory (image information storing means) 24, a control 
unit (control means) 25 and a bus 26 connected to each of the components 
provided in the apparatus 2. The external line interfaces A.sup..multidot. 
I/F.sub.1 through A.sup..multidot. I/F.sub.m are connected to the 
plurality of external lines LO.sub.1 through LO.sub.m, respectively and 
also to the switching unit 21, and they are in charge of inputting and 
outputting of analog signals. The internal line interfaces 
B.sup..multidot. I/F.sub.1 through B.sup..multidot. I/F.sub.n are 
connected to the plurality of internal lines LI.sub.1 through LI.sub.n, 
respectively, and also to the switching unit 21, and they are in charge of 
inputting and outputting of analog signals. It is to be noted that the 
external line interfaces A.sup..multidot. I/F.sub.1 through 
A.sup..multidot. I/F.sub.m and the internal line interfaces 
B.sup..multidot. I/F.sub.1 through B.sup..multidot. I/F.sub.n are provided 
with tone signal detectors and off-hook detectors so that they detect 
various tone signals and off-hook conditions to thereby supply detection 
signals to the control unit 25. 
The switching unit 21 is connected to the external line interfaces 
A.sup..multidot. I/F.sub.1 through A.sup..multidot. I/F.sub.m, to the 
internal line interfaces B.sup..multidot. I/F.sub.1 through 
B.sup..multidot. I/F.sub.n, to the facsimile communication units F.sub.1 
through F.sub.x, and also to the tone generator 22, so that the switching 
unit 21 controls an operative coupling between these components. Each of 
the facsimile communication units F.sub.1 through F.sub.x is provided with 
a MODEM, a compression/decompression unit, and a 2K byte double buffer 
memory. Thus, the image information received from a transmitter at a 
remote station is demodulated, decompressed and stored into one of the two 
buffer memories, and, as soon as the memory has become full, the image 
data thus stored therein is transferred to the memory 25 (input 
operation). On the other hand, the image information transferred from the 
memory 25 is stored into one of the two memories of the double buffer 
memory, and the image information is supplied to a terminal unit after 
demodulation (output operation). 
The tone generator 22, as shown in FIG. 3, includes a first DT generator 
31, a second DT generator 32, a third DT generator 33, a fourth DT 
generator 34, a RBT generator 35, a BT generator 36 and a howler sound 
generator 37. The DT generators 31 through 34 generate dial tones, for 
example, such as those shown in FIGS. 4a through 4d. That is, the first DT 
generator 31 outputs a continuous tone of 800 Hz and the second DT 
generator 32 outputs a tone of 800 Hz continuous for one second at 0.5 
second intervals. The third DT generator 33 outputs a tone of 800 Hz 
continuous for 0.5 seconds at one second intervals, and the fourth DT 
generator 34 outputs a tone of 800 Hz continuous for 0.5 seconds at 0.5 
second intervals. The RBT generator 35 generates a ring back tone (RBT) 
shown in FIG. 4e and the BT generator 36 generates a busy tone (BT) shown 
in FIG. 4f. The howler sound generator 37 generates a howler sound 
(abnormal condition indicating sound) shown in FIG. 4g. 
Returning to FIG. 2, the memory 24 stores image information supplied from a 
terminal unit in the form of a file according to a designated destination 
to which the image information is to be transmitted, and thus the memory 
24 also stores such information as the name of designated destination, its 
telephone number and various other management information. The control 
unit 25 controls the switching unit 21, tone generator 22, memory 24, 
external line interfaces A.sup..multidot. I/F.sub.1 through 
A.sup..multidot. I/F.sub.m, internal line interfaces B.sup..multidot. 
I/F.sub.1 through B.sup..multidot. I/F.sub.n and facsimile communication 
units F.sub.1 through F.sub.x to thereby cause the store and forward 
switching type communication control apparatus 2 to carry out a sequence 
of steps relating to a resource status examination process in accordance 
with one aspect of the present invention. 
In operation, the store and forward switching type communication control 
apparatus 2 has two modes of operation, i.e., (1) direct communication 
mode, in which a communication is carried out among the internal lines 
LI.sub.1 through LI.sub.n or a switching operation is carried out between 
the internal lines LI.sub.1 through LI.sub.n and the external lines 
LO.sub.1 through LO.sub.m, and (2) store and forward communication mode, 
in which image information supplied to the store and forward switching 
type communication control apparatus 2 from one of the facsimile machines 
FI.sub.1 through FI.sub.n connected to the internal lines LI.sub.1 through 
LI.sub.n or the the external lines LO.sub.1 through LO.sub.m is once 
stored in the memory 24 of the store and forward switching type 
communication control apparatus 2 and then the thus stored image 
information is read out at an appropriate timing from the memory 24 to be 
transmitted to a destination which may be one of the facsimile terminal 
units FI.sub.1 through FI.sub.n. 
In accordance with the principle of the present invention, when one of 
terminal units, which may be either telephone units or facsimile units, 
FI.sub.1 through FI.sub.n connected to the internal lines LI.sub.1 through 
LI.sub.n is off-hooked, the present status or availability condition of 
the resources of the store and forward switching type communication 
control apparatus 2 which are available to the internal lines LI.sub.1 
through LI.sub.n is first examined and its result is apprised to the 
operator before an input operation is carried out by the operator, so that 
the operator is prevented from carrying out an invalid input operation 
since the availability condition of the resources is indicated to the 
operator before the operator carries out an input operation. 
Hereinafter, with particular reference to the flow chart shown in FIGS. 5A 
and 5B, the resource status examination process will be described in 
detail. When one of the telephone units or facsimile units FI.sub.1 
through FI.sub.n connected to the internal lines LI.sub.1 through LI.sub.n 
is off-hooked (step P.sub.1), the control unit 25 examines whether or not 
the external line interfaces A.sup..multidot. I/F.sub.1 through 
A.sup..multidot. I/F.sub.m are available (step P.sub.2) and whether or not 
the facsimile communication units F.sub.1 through F.sub.x are available 
(step P.sub.3). Then, based on the availability condition of the 
resources, the control unit 25 selects one of the first through third DT 
generators 31 through 33 of the tone generator 22 in accordance with the 
availability condition of the resources (in the illustrated embodiment, 
external line interfaces A.sup..multidot. I/F.sub.1 through 
A.sup..multidot. I/F.sub.m and facsimile communication units F.sub.1 
through F.sub.x) of the store and forward switching type communication 
control apparatus 2 (step P.sub.4). That is, as shown in the table below, 
if both of the external line interfaces A.sup..multidot. I/F.sub.1 through 
A.sup..multidot. I/F.sub.m and the facsimile communication units F.sub.1 
through F.sub.x are available (OK), the first DT generator 31 is selected 
(step P.sub.5). If the external line interfaces A.sup..multidot. I/F.sub.1 
through A.sup..multidot. I/F.sub.m are available (OK), but the facsimile 
communication units F.sub.1 through F.sub.x are not available (NG), then 
the second DT generator 32 is selected (step P.sub.6). And, if the 
external line interfaces A.sup..multidot. I/F.sub.1 through 
A.sup..multidot. I/F.sub.m are not available (NG) and the facsimile 
communication units F.sub.1 through F.sub.x are available (OK), then the 
third DT generator 33 is selected (step P.sub.7). And, if neither the 
external line interfaces A.sup..multidot. I/F.sub.1 through 
A.sup..multidot. I/F.sub.m nor the facsimile communication units F.sub.1 
through F.sub.x are available (NG), then the fourth DT generator 34 is 
selected (step P.sub.8). 
TABLE 
______________________________________ 
1st DT 2nd DT 3rd DT 4th DT 
Generator Generator Generator 
Generator 
31 32 33 34 
______________________________________ 
External OK OK NG NG 
Line 
Interface 
Facsimile 
OK NG OK NG 
Communi- 
cation 
Unit 
______________________________________ 
Then, the control unit 25 designates to the switching unit 21 a connection 
between one of the first through fourth DT generators 31 through 34 of the 
tone generator 22 which has been selected by the above-described 
processing and one of the internal line interfaces B.sup..multidot. 
I/F.sub.1 through B.sup..multidot. I/F.sub.n which corresponds to the 
off-hooked one of the internal lines LI.sub.1 through LI.sub.n (step 
P.sub.9). When such a connection has been established, a dial tone 
generated by the thus selected DT generator is output to the internal line 
LI.sub.1 through LI.sub.n. Depending on the kind of the dial tone thus 
received, the operator at the terminal unit will know the availability 
condition of the resources of the store and forward switching type 
communication control apparatus 2. For example, if the dial tone thus 
received is from the first DT generator 31, the operator will know that 
facsimile communication is also available. If it is the dial tone from the 
second DT generator 32, the operator will know that facsimile 
communication is not available, but telephone communication is available. 
If the dial tone received is from the fourth DT generator 34, the operator 
will know that he or she must wait until some resources become available 
because there is no available resources right at the moment. As a result, 
in accordance with the present invention depending on the kind of the dial 
tone received, the operator can determine the availability condition of 
the resources of the store and forward switching type communication 
control apparatus 2 and then whether or not to carry out a next step, such 
as dialing operation or facsimile transmission operation. Thus, the 
operator is prevented from carrying out an input operation in the case 
where there is no available resources. 
Then, when a dialing operation is carried out (step P.sub.10), the control 
unit 25 designates a release of a connection between the tone generator 22 
and the internal line interfaces B.sup..multidot. I/F.sub.1 through 
B.sup..multidot. I/F.sub.n to the switching unit 21 (step P.sub.11) and 
waits for an operational instruction supplied through one of the internal 
lines LI.sub.1 through LI.sub.n (step P.sub.12). If the operational 
instruction supplied indicates a direct communication mode, the external 
line interfaces A.sup..multidot. I/F.sub.1 through A.sup..multidot. 
I/F.sub.m are secured (step P.sub.13), and when they are secured, i.e., 
set in the state of "OK", (step P.sub.14), a sequence of steps of the 
ordinary direct communication mode is carried out (step P.sub.15). If the 
external line interfaces A.sup..multidot. I/F.sub.1 through 
A.sup..multidot. I/F.sub.m have not been secured at step P.sub.14 (NG), 
the DBT generator 36 of the tone generator 22 is connected to the internal 
line interfaces B.sup..multidot. I/F.sub.1 through B.sup..multidot. 
I/F.sub.n of the internal lines LI.sub.1 through LI (step P.sub.16), and 
then the transmission line is disconnected (step P.sub.18) as soon as the 
internal lines LI.sub.1 through LI.sub.n have been on-hooked (step 
P.sub.20). 
On the other hand, if the direct communication mode has been designated at 
step P.sub.12, securing of the facsimile communication units F.sub.1 
through F.sub.x is designated (step P.sub.19), and, upon securing (step 
P.sub.20), a sequence of the normal store and forward communication mode 
is carried out (step P.sub.21). If the facsimile communication units 
F.sub.1 through F.sub.x have not been secured at step P.sub.20, it 
proceeds to step P.sub.16 to apprise of this fact to the operator to 
thereby carry out a similar process (steps P.sub.16 through P.sub.18). 
In the above-described embodiment, it is so structured that, when an 
off-hook state has been created at one of the internal lines, the 
availability status of the resources is examined and the result of its 
examination is supplied to the internal line, whereby securing of the 
resources is carried out in response to an operational instruction 
supplied from the internal line. However, the present invention should not 
be limited only to such a specific structure, and it may also be so 
structured that securing of resources is carried out simultaneously with 
the examination of resources as soon as an off-hook status has been 
created. A sequence of steps in this mode of operation is illustrated in 
the form of a flow chart in FIGS. 6A and 6B and its sequence will be 
described below with particular reference to the flow chart shown in FIGS. 
6A and 6B. It is to be noted that since the sequence of steps shown in the 
flow chart of FIGS. 5A and 5B is similar in many respects to that of the 
flow chart shown in FIGS. 6A and 6B, like steps are indicated by like 
reference numerals and repetitive description will be avoided. 
When one of the internal lines LI.sub.1 through LI.sub.n has been 
off-hooked (step P.sub.1), the control unit 25, in the first place, 
designates to secure the external line interaces A.sup..multidot. 
I/F.sub.1 through A.sup..multidot. I/F.sub.m (step S.sub.1) and confirms 
the securing condition of the external line interfaces A.sup..multidot. 
I/F.sub.1 through A.sup..multidot. I/F.sub.m (step S.sub.2). Then, it is 
designated to secure the facsimile communication units F.sub.1 through 
F.sub.x (step S.sub.3) and the secured condition of the facsimile 
communication units F.sub.1 through F.sub.x is confirmed (step S.sub.4). 
Depending on the secured condition of the external line interfaces 
A.sup..multidot. I/F.sub.1 through A.sup..multidot. I/F.sub.m and the 
facsimile communication units F.sub.1 through F.sub.x, i.e., the current 
availability status of the resources, one of the dial toner generators 31 
through 34 of the tone generator 22 is selected (steps P.sub.4 through 
P.sub.8) in a manner similar to the previously described embodiment to 
thereby output the dial tone of the thus selected dial tone generator, one 
of 31 through 34, to a corresponding one of the internal lines LI.sub.1 
through LI.sub.n (step P.sub.9). Depending on the kind of the dial tone 
thus received, the operator will know the secured condition or current 
availability condition of resources. As a result, the operator is 
prevented from carrying out an invalid inputting operation. In addition, 
in accordance with this embodiment, since the required resources have 
already been secured, the operator can implement the subsequent operation 
at ease. 
Then, the operator inputs an operational instruction, and if it indicates 
the direct communication mode, the control unit 25 designates a release of 
the facsimile communication units F.sub.1 through F.sub.x (step S.sub.5) 
so that a sequence of the ordinary direct communication mode is carried 
out (step P.sub.15). On the other hand, if the operational instruction 
given by the operator indicates the store and forward communication mode, 
the release of the external line interfaces A.sup..multidot. I/F.sub.1 
through A.sup..multidot. I/F.sub.m is designated (step S.sub.6), whereby a 
sequence of the ordinary store and forward communication mode of operation 
is carried out (step P.sub.21). 
As described above, in accordance with the present invention, since the 
current availability status or condition of the resources is apprised to 
the operator when the operator has established an off-hook status at one 
of the terminal units connected to the internal lines of the store and 
forward switching type communication control apparatus prior to any input 
operation by the operator, any invalid input operation is prevented from 
being carried out by the operator. Thus, there is provided an improved 
store and forward switching type communication control apparatus high in 
operability and efficiency. 
While the above provides a full and complete disclosure of the preferred 
embodiments of the present invention, various modifications, alternate 
constructions and equivalents may be employed without departing from the 
true spirit and scope of the invention. Therefore, the above description 
and illustration should not be construed as limiting the scope of the 
invention, which is defined by the appended claims.