JP3257479B2 - Dial-in terminal device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for receiving a call in response to a dial-in call, outputting a pseudo-call signal to a communication terminal to which the called dial number is assigned, and calling the communication terminal. The present invention also relates to an improvement of a terminal device having a dial-in exchange function for automatically connecting the communication terminal to a telephone line.

[0002]

2. Description of the Related Art This type of dial-in terminal device connects a plurality of communication terminals assigned with a dial-in number to one telephone line and receives a predetermined call (dial-in call) from a telephone exchange. A switching function is provided to output a pseudo call bell to the called communication terminal and, when the communication terminal responds, connect the responding communication terminal to a telephone line to respond.

FIGS. 5A and 5B are time charts showing a calling operation in a currently used dial-in service. FIG. 6 shows a facsimile apparatus having a modem and having a dial-in function. It is shown with a block diagram. Referring to these drawings, in the dial-in service, when a dial-in call is received from a telephone exchange, the following control is performed.

That is, when the dial-in terminal apparatus 100 receives a calling signal from the telephone exchange via the telephone line L, it closes the line relay 101, closes the DC circuit, receives an incoming call, and pushes the subsequently transmitted DTMF signal. The signal is received by the signal detection circuit 102. When the reception of the DTMF signal is completed, the S relay is closed, the modem 106 is short-circuited, and the line relay 101 is opened to open the once closed DC circuit, and the DC cutoff connected in parallel to the line relay 101 is opened. The capacitor C is connected to close the AC circuit. While maintaining this state, the signal processing unit (not shown) decodes the DTMF signal and switches the switching relay 103a from the telephone line L to the pseudo call signal generation circuit 104.
Side (closed on the a side), and the false call signal generation circuit 104
To make a pseudo call. Then, the communication terminal TEL
When one of the communication terminals TEL1 and 2 lifts up the handset and responds, the exchange relay 103a is switched back to the telephone line L (closed at the side b) and a call is made from an outside line. Talking and communication with the communication terminal that performed the communication become possible.

By the way, in such a dial-in terminal device 100, after a call signal from an outside line is received by the call signal detection circuit 103, the line relay 101 is closed and the call is received,
While the communication terminals TEL1 and TEL2 are being pseudo-called, the line relay 101 is opened, the S relay S is closed instead, and a DC cut capacitor C connected in parallel to the line relay 101 is connected to connect the AC terminal. With the circuit closed
A pseudo call is made to the communication terminals TEL1 and TEL2.

Therefore, if a caller stops calling from an outside line by placing a handset or the like during the pseudo call, the telephone exchange opens the telephone line. At this time, since the pulse change occurring in the AC circuit is small (generated by discharging the electric charge charged in the DC cut capacitor), even if the polarity inversion detection circuit 105 detects the pulse change, the signal processing unit detects the state change. Often overlooked.

However, if the signal processing unit misses such a change, the pseudo call signal generation circuit 104 has already been activated, and any of the communication terminals TEL1 and TEL2 that are sounding the pseudo call bell. Pick up the handset and let it respond once.
Unless it is detected by the above, the signal processing unit cannot stop the pseudo call, and there is a problem that the state where the pseudo call bell is output is left as it is.

[0008]

SUMMARY OF THE INVENTION The present invention reliably detects the above-mentioned problem in the conventional dial-in communication terminal device, that is, the call stopping operation of the caller during the period during which the pseudo call is being performed. It is a first object of the present invention to provide a dial-in terminal device in which the ringing of the pseudo call bell is not unnecessarily continued.

A second object of the present invention is to propose a dial-in terminal device capable of detecting operations such as closing, opening, and reversing the polarity of a DC circuit at the time of incoming call, telephone call, and communication by a simple method without overlooking it. It is in.

[0010]

In order to achieve the above object, a dial-in terminal device according to the present invention comprises a polarity reversal detection circuit provided on an internal line constituting a closed circuit with a telephone exchange. And a pulse width expansion circuit is additionally connected to the output side of the polarity inversion detection circuit, and the expanded pulse is input to the signal processing unit. In the dial-in terminal device according to claim 2, the polarity inversion detection circuit is configured by a pair of photocouplers connected in anti-parallel, and the pulse width expansion circuit is activated when each of the pair of photocouplers is activated. The configuration is such that a trigger circuit for outputting a voltage pulse and a monostable multivibrator each triggered by the output of the trigger circuit are combined.

A dial-in terminal device according to a third aspect of the present invention includes a logical sum circuit for obtaining a logical sum output of a set of monostable multivibrators of a pulse width extending circuit, and outputs an output of the logical sum circuit to the signal processing unit. In addition to the input, the output from one of the photocouplers of the polarity inversion detection circuit is input to the signal processing unit, and the signal processing unit is opened if both the outputs of the OR circuit and the photocoupler are at the H level, and the OR circuit When both the output of the photo-coupler and the output of the photocoupler are at L level, it is determined that the DC is closed, and when the output of the OR circuit is at L level, the polarity is inverted.

[0012]

Embodiments of the present invention will be described below. FIG. 1 shows a basic configuration of a dial-in terminal device incorporating a polarity inversion circuit which is a main part of the present invention. Since the dial-in calling operation is the same as that of the above-described conventional device, the details are omitted.

As the dial-in terminal device A, a facsimile device provided with a modem 6 is applied. A connection terminal T is provided at one end of the internal line 10, and the connection terminal T is connected to a telephone connected to a telephone exchange. Connected to line L. Reference numeral 1 denotes a CML relay constituting a line relay. When a call signal from a telephone exchange is detected by a call signal detection circuit 2, the line relay 1 is closed, and at this time, an S relay S keeps an open state. Internal line 10 is a resistor R
b and Rc are connected in series, and the DC circuit is closed.

On the other hand, when the communication terminals TEL1 and TEL2 to which the dial-in numbers are assigned are in a standby state,
The exchange relay 7 is closed on the telephone line L side (closed on the b side) and connected to the telephone line L. When the DC circuit is closed in this manner, one of the photocouplers PH1 and PH2 connected in the forward direction out of the set of photocouplers PH1 and PH2 is driven. In addition, VS is a varistor for eliminating a spark generated when the line relay 1 and the S relay S are opened and closed, and Rd is a current limiting resistor of the photocouplers PH1 and PH2.

Next, the telephone exchange sends out a DTMF signal designating the dial-in number to the telephone line L. When the push signal detecting circuit 4 receives the DTMF signal, a signal processing unit constituted by a CPU or the like is provided. (Not shown)
Opens the line relay 1 to open the closed DC circuit,
Next, the S relay S is closed. As a result, the modem 6 is short-circuited by the S relay S, and the DC cut capacitor C and the resistance Ra connected in parallel to the line relay 1 are connected to the internal line 1.
Since it is connected to 0, the DC circuit is open and the AC circuit is closed instead.

The signal processing section holds this state, closes the exchange relay 7 to the pseudo call signal generation circuit 5 side (a side close), activates the pseudo call signal generation circuit 5, and activates the called communication terminal. Call TEL1 and TEL2 and ring the pseudo bell. Thus, when one of the communication terminals TEL1 and TEL2 called by the dial-in number responds by picking up the handset or the like, the communication terminal TEL1
Alternatively, hook detection circuits OH, OH provided on the TEL2 side
Detects the off-hook state, the signal processing unit communicates with the communication terminal TEL1 or T
The exchange relay 7 of EL2 is switched to the telephone line L side (b side closed), and the communication terminal TEL1 receiving the dial-in call
Alternatively, TEL2 is connected to the telephone line L to enable a telephone call.

By the way, in the dial-in communication terminal device which performs such a basic operation, when the caller hooks on and stops the call during the period of the pseudo call, the telephone exchange opens the telephone line L. Therefore, at this time, the charge charged in the DC cut capacitor C is also rapidly discharged, and the discharged current drives one of the photocouplers PH1 and PH2 in the forward direction. However, the electric charge discharged at this time is small, and the pulse signal output at the time of driving the photocouplers PH1, PH2 is often overlooked because the interrupt timing sampled by the signal processing unit is short. For this reason, the signal processing unit often misses the change at this time. In such a case, the pseudo call signal generation circuit 5 is kept in the operating state. Instead, the ringing bells of the communication terminals TEL1 and TEL2, which have been called, continue to ring.

In the present invention, in order to prevent such a problem from occurring, the photocoupler PH constituting the polarity inversion detecting circuit 3 is used.
1 and PH2, a pulse width expansion circuit 4 is additionally connected so that when one of the photocouplers PH1 and PH2 is driven, a pulse signal having a large fixed width is obtained, and the operation change is reliably performed in the signal processing unit. To be detected.

Referring to the embodiment shown in FIG.
, A pair of photocouplers PH1 and PH2 are connected in anti-parallel to form a polarity reversal detection circuit 3, and a pair of photocouplers PH1 and PH2 are connected to a trigger circuit 4141, respectively. Pulse width expansion circuit 4 combining two multivibrators M1 and M2
Is additionally connected.

More specifically, referring to the drawings, pull-up resistors R, R, which supply constant voltage power sources V, V, are connected to the output lines of a pair of photocouplers PH1, PH2, respectively. The trigger circuits 41, 41 are configured to input voltage pulses generated when the photocouplers PH1, PH2 are driven to the input terminals of the monostable multivibrators M1, M2, and to input the monostable multivibrators M1, M2.
From M2, Q determined by the external circuit (not shown)
An output signal (inverted signal) is output and input to the signal processing unit.

According to such a configuration, the photocoupler PH
1 or PH2 is turned on, the voltage held at the constant level V, V by the pull-up resistors R, R is reduced to the GND level. Vibrator M1, M
2 is started, and a voltage signal having a constant pulse width set by the time constant of the external circuit is output to the Q 1 and Q output terminals of the multivibrators M1 and M2.

Therefore, according to the configuration provided with such a pulse width extending circuit 4, when the DC circuit is closed or
When the AC circuit is closed or opened, the internal circuit 10
If a current change occurs, the change is output as a pulse signal having a constant width, so that the signal processing unit detects the change even if the interrupt timing for sampling is short, even if the interrupt timing for sampling is short. The signal processing unit can detect the signal, and therefore, even when the calling operation from the outside line is stopped during the period in which the AC closed state is held and the pseudo calling operation is performed, the signal processing unit can accurately detect the state. Since the detection can be performed, the unnecessary calling operation by the pseudo bell can be stopped.

FIGS. 2A to 2F are time charts showing the output of the pulse width expansion circuit according to the basic operation of the photocoupler. (A) and (b) show operations in which photocouplers PH1 and PH2 are turned on and off alternately by a current flowing through the internal line 10, and (c) and (d) show operations of a monostable multivibrator constituting a pulse width extending circuit. Trigger operation, (e) and (f) are monostable multivibrators M1,
This shows the Q output of M2. In the monostable multivibrator, when a trigger pulse is input by driving the photocoupler, a pulse signal having a constant width T is output at the falling edge.

Next, a more detailed embodiment of the present invention will be described. FIG. 3 also shows an example of application to a facsimile apparatus. Since the basic configuration is the same as that of the device shown in FIG. 1, the corresponding portions are denoted by the same reference numerals and description thereof will be omitted. Photocouplers PH1 and PH2 are connected to the internal line 10 in anti-parallel, and its output line is connected to a trigger circuit 4 composed of pull-up resistors R and R to which constant voltage power supplies V and V are supplied.
1 and 41, and the multivibrators M1 and M2 are connected to the trigger circuits 41 and 41, respectively. The cathodes of the diodes D1 and D2 are connected to the Q output terminals of the multivibrators M1 and M2, and the anodes of the diodes D1 and D2 are connected in common to supply a constant voltage power V. The OR circuit 42 is formed by connecting the pull-up resistor R, and the OR output of the multivibrators M1 and M2 is obtained.

That is, an output pulled up to a constant voltage level V by a pull-up resistor R connected to the photocoupler PH1 is output as a first determination signal DSE1,
The output of the OR circuit 42, which has been pulled up to a constant voltage level V by another pull-up resistor R, is output to a second determination signal D.
It is output as SE2. Therefore, according to such a circuit configuration, a basic operation as shown in FIG. 4 is performed for a dial-in call.

That is, when the call signal detection circuit 2 detects a call from an outside line, the line relay 1 (CML relay) is closed and a call is received. At this time, one of the photocouplers PH1 and PH2 is turned on and the other is turned off in accordance with the polarity of the closed DC circuit. For example, considering the case where the photocoupler PH1 is turned on and PH2 is turned off, the trigger circuit 41 connected to the photocoupler PH1 reduces the voltage level held at the constant level V by the pull-up resistor R to the GND level. , Multivibrator M1
Is triggered by its fall, and outputs a pulse signal (L level) of a predetermined width T as a Q output, but the other multivibrator M2 is not triggered, so that no pulse signal is output and the Q output is held at an H level. I do.

As a result, the first discrimination signal DES1 is output as L level while the ON state of the photocoupler PH1 remains unchanged, and the second discrimination signal DSE2 is output as the Q output (L level) of the multivibrator M1. Therefore, the signal processing unit determines that the photocoupler PH1 is turned on and the DC circuit is closed. Then, when the line relay 1 is opened and the S relay S is closed, the internal line 10 is connected to the DC cut capacitor C and becomes AC closed.
The photocoupler PH1 is turned on only during the first period of charging the capacitor C, and the other photocoupler PH2 remains off. Therefore, at the first time point when the S relay S is closed and the AC circuit is closed, the photocoupler PH1 is turned on only during the period when the capacitor C is charged. When the photocoupler PH1 is turned on, the multivibrator M1 is also triggered.
Outputs a pulse signal (L level) having a predetermined width T as a Q output.

On the other hand, since the photocoupler PH2 is turned off at this time, the Q output of the second multivibrator M2 keeps the H level, so that the second discrimination signal DS
In E2, the Q output of the multivibrator M1 is output as it is, and the signal processing unit determines that the AC circuit is closed by turning on the photocoupler PH1 after the S relay S is closed.

While the AC circuit is closed, the simulated ringing signal generating circuit 5 is operated so that the ringing bells of the communication terminals TEL1 and TEL2 to be ringed continue to ring (by the false ringing). Calling operation). However, if the calling party hooks on during such a calling operation, the telephone exchange cuts off the connection of the telephone line L, and the AC circuit is also opened at this time. Then, the electric charge charged in the DC cut capacitor C is discharged, and at that moment, the photocoupler PH2 is turned on (at this time, the photocoupler PH1 is turned off).
Is triggered to output a pulse signal (L level) having a predetermined width T. Therefore, even if the pseudo call operation is stopped halfway, the change at this time is caused by the multivibrator M2.
In the signal processing section, this change can be detected without overlooking it, and the pseudo call signal generation circuit 5 can be stopped to stop the pseudo bell.

Therefore, according to such a circuit configuration, the first determination signal DSE1 (L level) is a signal for detecting that the photocoupler PH1 has been turned on, and the second determination signal DSE2 (L level). Is a signal for detecting that one of the photocouplers PH1 and PH2 has been turned on. When the second discrimination signal DSE2 is inverted to L level, the level of the first discrimination signal DSE1 is checked. , Any set of photocoupler PH
Since it is easy to determine which one of PH1 and PH2 is turned on, in the signal processing unit, if the operation is combined with the operation of the line relay 1 and the S relay S, the internal line 10 is DC closed or opened. That the exchange was closed,
Alternatively, it can be determined that the AC connection has been released, and the operation such as closing, opening, and reversing the polarity of the DC circuit during incoming call, telephone call, or communication can be detected by a simple method without being overlooked. For example, when the second determination signal DSE2 becomes L and the first determination signal DSE1 is L, the photocoupler PH1 is inverted to ON and the first determination signal DSE1 becomes H
, It is understood that the photocoupler PH2 has been turned on, and the first determination signal DSE1 and the second determination signal DSE1
If both DES1 and DES2 are H, it is understood that the internal line 10 is open.

The provision of the above-mentioned OR circuit 42 has the advantage that when the telephone line is connected to the telephone exchange, the connection can be made without considering the polarity of the DC circuit to be closed.

[0032]

According to the first aspect of the present invention,
When a current change occurs in the internal line connected to the telephone line and the polarity inversion circuit detects the change, the pulse signal is extended to a pulse signal of a fixed width by the pulse width expansion circuit and output. Even a slight change in current generated in the line can be detected. Therefore, even in the case where the pseudo call of the caller is stopped during the pseudo call period in which the extension circuit holds the AC closed state, the state can be accurately detected even if the call source is stopped, and the unnecessary call operation by the pseudo bell is prevented. Can be stopped.

According to the present invention described in claim 2,
The same function as that of claim 1 can be realized with a simple configuration in which only one set of a photocoupler, a trigger circuit, and a monostable multivibrator are combined. Further, according to the present invention, when connecting to a telephone line, the connection can be performed without considering the polarity of the DC circuit closed when connected to the telephone exchange.

[Brief description of the drawings]

FIG. 1 is a block diagram of a dial-in terminal device according to an embodiment of the present invention.

FIG. 2 is a time chart showing a basic operation of a polarity inversion circuit in the dial-in terminal device.

FIG. 3 is a block diagram of a dial-in terminal device showing another example of the present invention.

FIG. 4 is a time chart showing a basic operation of another example of the polarity inversion circuit.

FIGS. 5A and 5B are time charts showing a basic operation of dial-in calling.

FIG. 6 is a block diagram showing a conventional dial-in terminal device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Line closing relay 2 ... Paging signal detection circuit 3 ... Polarity reversal detection circuit 4 ... Pulse width expansion circuit 41 ... Trigger circuit 42 ... OR circuit PH1, PH2 ...・ Photocoupler M1, M2: Multivibrator L: Telephone line 10: Internal line

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04Q 3/58 105 H04M 1/00 H04M 11/00 303

Claims (3)

(57) [Claims] In a dial-in terminal device, a polarity reversal detection circuit provided on an internal line forming a closed circuit with the telephone exchange, and a pulse width expansion circuit added to an output side of the polarity reversal detection circuit. A dial-in terminal device which is connected and inputs an expanded pulse to a signal processing unit. 2. The apparatus according to claim 1, wherein said polarity reversal detection circuit comprises a pair of photocouplers connected in anti-parallel, and said pulse width expansion circuit operates when each of said pair of photocouplers is activated. And a monostable multivibrator each of which is triggered by an output of the trigger circuit. 3. The signal processing section according to claim 2, further comprising: a logical sum circuit for obtaining a logical sum output of a set of monostable multivibrators of said pulse width extending circuit; Inputting an output from one of the photocouplers of the polarity reversal detection circuit to the signal processing unit, wherein the signal processing unit is open if both the outputs of the OR circuit and the photocoupler are at the H level; A dial-in terminal device, which determines that the DC connection is established when both the output of the OR circuit and the output of the photocoupler are at L level and that the polarity is inverted when the output of the OR circuit is at L level.