JP2936774B2 - Telephone equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telephone device for releasing a hold or confidential alarm when a telephone line terminal is provided with another line terminal.

[0002]

2. Description of the Related Art Conventionally, this type of telephone device stores a line voltage applied to one telephone device in a capacitor when a line of one telephone device is closed, and a line terminal attached thereto is connected to an off-hook of the other telephone device. A sudden change in the line voltage that occurs when the line terminal is closed due to an interruption is detected, or another line terminal is connected via the one telephone device.

FIGS. 10 and 1 show a main part of a conventional telephone apparatus of this type and a configuration of connection with a line of the telephone apparatus.
1 will be described.

FIG. 10 shows a first conventional example. In FIG. 10, reference numeral 101 denotes a telephone device A, reference numeral 102 denotes a telephone device B, and even if the telephone device B102 has the same circuit configuration as the telephone device A101, the telephone device has a simple configuration such as a 600-type telephone. There may be. 103 is a line. Inside the telephone device, 104 is the plus side, 105
Is the minus side. 106 is a diode group,
Whichever polarity the telephone device A101 is connected to the line 103, the plus side 104 always acts positively and the minus side acts negatively. 107 and 108 are resistors, 109 is a diode, 110 is a transistor, 11
1 is a control circuit, 112 is a capacitor. Reference numeral 113 denotes a hold circuit, which is driven by the control circuit 111.

Next, the operation of this conventional example will be described.
In FIG. 10, while the line is closed, a current supplied from the line 103 is input to the base of the transistor 110 via the diode group 106, the resistor 107, the diode 109, and the resistor 108, so that the transistor 110 is turned on. The “L” level is input to the control circuit 111. Here, when the line closing voltage sharply decreases, the electric charge charged in the capacitor 112 is discharged through the resistor 107, so that the transistor 110 is turned off momentarily, and the “H” level is input to the control circuit 111. Is done. When "H" is input from the transistor 110, the control circuit 111 determines that the attached line terminal has been taken off-hook, and drives the holding circuit 113 to release the holding.

FIG. 11 shows a second conventional example. In FIG. 11, reference numeral 114 denotes a telephone device C. Reference numeral 115 denotes a telephone device circuit, at least a diode group 106 shown in FIG.
Contains. 116 is a photocoupler, 117 is an LED in the photocoupler 116 connected in reverse, 11
8 is a phototransistor. An inverter 119 inverts the phase of the output of the phototransistor 118. Reference numeral 120 denotes an attached line, which is connected to the telephone device B102 via the LED 117 in the photocoupler 116 in the telephone device C114. Reference numeral 121 is a secret talk alarm circuit. Reference numerals 103, 111 and 113 have the same functions as the elements of the same reference numerals in the first embodiment.

Next, the operation of this conventional example will be described.
When the telephone device B 102 connected to the additional line 120 goes off-hook, that is, when the additional circuit 120 is closed, the current supplied from the line 103 flows to the LED 117 in the photocoupler 116, so that the phototransistor 118
Is turned on, and an “H” level is input to the control circuit 111 by the inverter 119. The control circuit 111 determines that the attached line terminal is in the on-hook state when the output of the phototransistor 118 is "L" and is off-hook when it is "H".

Thus, the second conventional example operates in the same manner as the first conventional example.

[0009]

However, in the above-mentioned conventional telephone apparatus, in the first conventional example shown in FIG. 10, a range of a fixed ratio due to on-hook or the like regardless of the level of the line voltage when the line is closed. Responded to the voltage drop inside. Also, it was not possible to detect a rise in line voltage. Therefore, since the control circuit 111 operates only under extremely limited line conditions such as low line resistance, it is not possible to detect the transition of the attached line terminal to off-hook, and the hold release and the confidential alarm function are not performed. Could not be realized.

In the second conventional example shown in FIG. 11, since a photocoupler is inserted in series with a line terminal provided in parallel, the voltage drop due to the resistance of the line and the forward voltage of the LED are added. There is a problem that not only the voltage supplied to the attached line terminal is reduced and adversely affected, but also other line terminal devices cannot be connected without the telephone device C114.

The present invention solves such a conventional problem, and can detect an off-hook or an on-hook without affecting an attached line terminal, and can detect when an attached terminal device interrupts during a call. It is an object of the present invention to provide an excellent telephone device capable of reliably releasing hold and generating a confidential alarm sound.

[0012]

According to the present invention, in order to achieve the above object, a first means is to use an AD converter and the AD converter.
Means for storing the output value of the converter in two stages by the first and second storage means, first timekeeping means, and initial setting means are provided to detect a change in the line closing voltage and to detect the change. The off-hook and on-hook of the line terminal attached to the base are determined. The second means is the third
Is provided, the output of the AD converter is read a plurality of times, and the average value is replaced with the line closing voltage. A third means is to provide an offset determining means for reading the output of the AD converter so as not to react to a subtle change. The fourth means is provided with a judgment table, and judges the validity of the change based on the data of the judgment table addressed by the value before and after the change of the circuit closing voltage. The fifth means is provided with a second time measuring means, which detects when the line closing voltage continuously falls below a certain value. A sixth means is to provide a voltage dividing means at the input of the AD converter so that a voltage higher than a certain level is not inputted to the AD converter. The seventh means is to prevent the output of the AD converter from being read as an invalid value during the operation of the dial transmission circuit, and to further start the first timer means. Further, in order to achieve another object, the eighth means is provided with means for detecting a change in the circuit closing voltage, and a secrecy warning output means, and outputs a secrecy warning based on the determination of the detection means. Things. Ninth
Means is provided with a hold button and a hold sound generating means, and when the hold button is operated, that is, when the line is put on hold, the confidential alarm output is stopped, and the confidential alarm output is not performed during the line hold. It is. The tenth means is provided with an alarm stop button, and if the above button is pressed during the output of the confidential alarm, the output of the confidential alarm is stopped.

[0013]

The present invention has the following effects due to the above-described configuration. The first means inputs the line closing voltage via the AD converter, and the first storage means and the first timing means determine that the input value is stable, and then store the input value in the second storage means, When the line closing voltage changes, the rise and fall of the line closing voltage are detected by comparing the value with the value stored in the second storage means. When the line closing voltage rises, the terminal device attached thereto goes on-hook. When it has decreased, it can be determined that it has gone off-hook. By averaging the output of the A / D converter by the second storage means and the counter by the third storage means, the AC component in the line closing voltage is removed. Actions can be taken. By the third means, when the change in the output value of the AD converter is small, it is determined that there is no change, so that it is possible to prevent unnecessary response to a slight change in the line closing voltage. In addition, by setting the offset value based on the value when the line closing voltage is in a stable state, when the line closing voltage is high, it is considered that the attached terminal has changed when there is a large voltage change, and the line closing In a state where the voltage is low, it can be considered that a change in the attached terminal has occurred even with a small voltage change, and a more accurate determination can be made. In this case, if the change in the line voltage is smaller than the above-mentioned offset value, the change is regarded as not the change information of the co-located terminal. But don't misjudge. According to the fourth means, the same effect as that of the third means can be obtained by setting the data of the determination table, and the difference from the circuit closing voltage before and after the change or the offset value can be calculated from the determination table without calculating the offset value. This has the effect that the user can immediately judge a change in the attached terminal from the data. According to the fifth means, when the line closing voltage becomes lower than a predetermined value for a certain period of time or longer, it is determined that the line power is in a cut-off state. The line closing operation can be ended. According to the sixth means, even when the line closing voltage becomes higher than the input allowable voltage of the AD converter, the AD converter can be operated normally. By the seventh means,
It is possible to prevent the user from seeing the voltage change during dial transmission and immediately start monitoring the line closing voltage change after dialing is completed. By outputting the confidential alarm to the caller by the eighth means, the line terminal attached is off-hook,
It can notify that there is a possibility of eavesdropping or the like. By the ninth means, it is possible to remove an unnatural state in which the hold sound and the confidential talk alarm operate simultaneously. According to the tenth means, by pressing this button while the confidential alarm is being output, the confidential alarm can be stopped and the three-party communication state can be set.

[0014]

FIG. 1 is a block diagram showing the configuration of an apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a control unit which is configured by a microcomputer and controls the entire apparatus. 2 is a line connection terminal. Reference numeral 3 denotes a circuit closing circuit, which is driven by the control unit 1. Reference numeral 4 denotes a speech network, 5 denotes a handset including a receiver and a microphone, 6 denotes a hold tone generation circuit, and 7 denotes a confidential alarm generation circuit. The hold sound generation circuit 6 and the confidential alarm generation circuit 7
And outputs it to the speech network 4.
A voltage dividing circuit 8 divides a line closing voltage. 9 is A
This is a D converter, which receives the line closing voltage divided by the voltage dividing circuit 8, converts it into a digital value, and outputs it. 10,
11 and 12 are first, second and third memories, respectively.
Reference numerals 3 and 14 denote first and second timers, 15 denotes a hold button, 16 denotes an alarm stop button, 17 denotes a judgment table,
Reference numeral 8 denotes a hook switch, and 19 denotes a dial operation button, which sends dial data to the control unit 1. Reference numeral 20 denotes a dial transmission circuit. When dial data is input from the control unit 1, the dial transmission circuit 20 transmits a dial to a line and always determines whether or not dial transmission is being performed.
Output to 21 is a counter. The output terminals of the control unit 1 are connected to a circuit closing circuit 3, a speech network 4,
Hold sound generation circuit 6, confidential alarm generation circuit 7, first memory 10, second memory 11, third memory 12, first timer 13, second timer 14, determination table 17, dial transmission circuit 20 And a counter 21 are connected. The input terminals of the control unit 1 include a hold button 15, an alarm stop button 16, a hook switch 18, a dial operation button 19, an AD converter 9, and a first memory 1.
0, the second memory 11, the third memory 12, the first timer 13, the second timer 14, the determination table 17, the dial transmission circuit 20, and the output of the counter 21 are connected.

Next, a specific embodiment will be described. (Embodiment 1) A first embodiment of the operation of the apparatus having the configuration shown in FIG. 1 will be described with reference to FIGS. 2, 3 and 4. FIG.

FIG. 2 is a flowchart showing the entire flow in the first embodiment of the operation. FIG. 3 is a flowchart showing details of the line monitoring operation among the steps included in FIG. FIG. 4 is a flowchart showing details of the line state determination operation among the steps included in FIG.

In FIG. 2, in an initial state, the control unit 1 monitors the state of the hook switch 18 in step 22. Here, when the handset 5 is picked up, it goes into an off-hook state, and the control unit 1 drives the line connection circuit 3 in step 23 to close the line. As a result, power for speech communication is supplied from the line to the speech network 4 via the line connection terminal 2 and the line closing circuit 3, and at the same time, a line closing voltage is input to the voltage dividing circuit 8. Also, the control unit 1 executes step 24
And the counter 21 and the three memories 10, 11 and 12
Is cleared to shift to the call state. In the call state, the control unit 1 monitors the hold button 15, the alarm stop button 16 and the dial operation button 19 in step 25, monitors the line state change in step 29, and monitors the state change of the hook switch 18 in step 33. ing. here,
When the control unit 1 determines in step 30 that the line terminal attached thereto has been off-hook due to a decrease in the line closing voltage, in step 31, the secret-tone warning generating circuit 7 is driven to output a secret-tone warning sound. When the control unit 1 determines that the line terminal attached thereto is on-hook due to the increase in the line closing voltage in step 30, the drive of the privacy alarm generation circuit 7 is stopped in step 32, and the output of the privacy alarm sound is performed. Stop. If the control unit 1 determines that the dial operation button 19 has been pressed in step 26 in the call state, the process proceeds to step 2.
At 7, the dial data is output to the dial transmission circuit 20. When the control unit 1 determines that the hold button 15 has been pressed in step 26 in the call state, the drive of the secret sound alarm generation circuit 7 is canceled in step 36, and the hold sound generation circuit 6 is driven in step 37 to generate the hold sound. Output and shift to the line hold state. In the line hold state, the control unit 1 monitors a state change of the line in step 38 and monitors a state change of the hook switch 18 in step 40. Here, if the control unit 1 determines in step 39 that the line terminal attached thereto has been off-hook due to a decrease in the line closing voltage, in step 41 the driving of the hold sound generation circuit 6 is canceled to stop the hold sound, and Release the hold status.

Here, the details of the monitoring operation of the line state change shown in step 29 and step 38 in FIG. 2 will be described with reference to FIG. The control unit 1 reads the state of the dial transmission circuit 20 in step 42, and if the dial transmission is in progress, clears and starts the first timer 13 in step 43. If no dialing is in progress, step 44
Reads the output value of the AD converter 9 at step 45
To judge the change of the line state.

The details of the operation for determining a change in the line state shown in step 45 of FIG. 2 will be described with reference to FIG. In step 46, the control unit 1 compares the read output value of the AD converter 9 with the value of the first memory 10.
If they are different, the first timer 13 is cleared and started in step 47, and the read value is written in the first memory 10 in step 48. If the values compared in step 46 match, the control unit 1 determines in step 49 that the first timer 1
Check the value of 3. If the value of the first timer 13 exceeds the predetermined value, the control unit 1
The value of the memory 11 is checked, and if cleared, the process proceeds to step 54. If it has not been cleared, the read output value of the AD converter 9 and the second memory 11
To the value of. At this time, if the output value of the AD converter 9 is larger, the control unit 1 determines that the line terminal provided in step 53 is on-hook, and if the value of the second memory 11 is larger, the control unit 1 Is Step 52
It is determined that the line terminal attached in the step has been hooked off.
Further, at step 54, the value of the first memory 10 is written to the second memory 11, and the process is terminated.

As described above, according to the first embodiment, A
The line closing voltage is input via the D converter 9 and stored in the second memory 11 after the input value is stabilized, and the value stored in the second memory 11 when the line closing voltage changes By comparing with the above, there is an advantage that it is possible to detect an increase or a decrease in the line closing voltage and determine the on-hook and the off-hook of the terminal device attached thereto. Also,
By outputting a confidential alarm to the caller based on this determination, it is possible to notify that there is a possibility of the line terminal attached to the terminal being off-hook and eavesdropping. Also,
When the hold button 15 is pressed, the drive of the confidential alarm generation means 7 is released, and the confidential alarm operation is prohibited during the hold, thereby eliminating the unnaturalness that the hold sound and the confidential alarm operate simultaneously. it can. Also, the alarm stop button 16
Is added, and when this button is pressed during the output of the confidential alarm, the driving of the confidential alarm generation circuit 7 is canceled, thereby providing an advantage that a three-party communication state can be established. Further, by compressing and inputting the line closing voltage within the input allowable voltage range of the AD converter 9 via the voltage dividing circuit 8, even when the line closing voltage becomes higher than the input allowable voltage of the AD converter 9, the A / D conversion is performed. There is an advantage that the converter 9 can operate normally. In addition, during the dial transmission, the output of the AD converter 9 is not read, and the first timer 13 is cleared and started. This has the advantage that detection can be newly started.

(Embodiment 2) A second embodiment of the operation of the apparatus having the configuration shown in FIG. 1 will be described with reference to FIG.

FIG. 5 is a flow chart of the main part showing the flow of the operation in the second embodiment, and FIG. 3 of the first embodiment.
Is a replacement for In the second embodiment, the control unit 1 reads the output of the AD converter 9 in step 55, adds the read value to the value in the third memory 12 in step 56, and writes the value in the third memory 12 as it is. In step 57, the counter 21 is incremented.
At step 58, the value of the counter 21 is checked, and if it is less than the set value, the monitoring process of the line state change is terminated. When the value of the counter 21 reaches the set value, the control unit 1 divides the value of the third memory 12 by the value of the counter 21 and divides this value into A
The output value of the D converter 9 is replaced with the third memory 12
And counter 21 are cleared in steps 60 and 61, respectively, and then the line state change determination operation in step 62 (FIG. 4)
Reference).

As described above, according to the second embodiment, the output of the AD converter 9 is averaged by the third memory 12 and the counter 21, and the AC component in the line closing voltage is removed. Therefore, there is an advantage that an accurate determination operation of the line state change can be performed using only the DC component.

(Embodiment 3) Next, a third embodiment of the operation of the apparatus having the configuration shown in FIG. 1 will be described with reference to FIG.

FIG. 6 is a flow chart of the main part showing the flow of the operation in the third embodiment, and FIG. 4 of the first embodiment.
Is a replacement for In the third embodiment, the control unit 1 calculates the difference between the output of the AD converter 9 read in step 44 of FIG. 3 and the value stored in the first memory 10 in step 63. Further, in Step 64, the control unit 1 compares the absolute value of the calculated value with the first offset value, and when the offset value is larger,
The output of the read AD converter 9 and the first memory 10
Are assumed to be the same, and the processing from step 49 onward in FIG. 4 is performed. If the offset value is smaller at step 64, it is considered that the read output of the AD converter 9 and the value of the first memory 10 are different from each other.
Step 47 and subsequent steps are performed.

According to the third embodiment, step 6
3, 64 constitute an offset determination means,
When the change in the output value of the AD converter 9 is small, it is determined that there is no change, so that there is an advantage that it is possible to prevent unnecessary response to a slight change in the line closing voltage.

(Embodiment 4) Next, a fourth embodiment of the operation of the apparatus having the configuration shown in FIG. 1 will be described with reference to FIG.

FIG. 7 is a flow chart of the main part showing the flow of the operation in the fourth embodiment.
Is a replacement for In the fourth embodiment, the control unit 1 compares the output of the AD converter 9 read in step 44 of FIG. 3 with the value stored in the first memory 10 in step 65. If they are different, the process from step 47 in FIG. 4 is performed. If the values compared in step 65 match, the control unit 1 checks the value of the first timer 13 in step 66. If the value of the first timer 13 has exceeded the predetermined value, the control unit 1 checks the value of the second memory 11 at step 67, and if it has been cleared, proceeds to step 74. If not cleared,
The control unit 1 calculates an offset value from the value in the second memory 11 in step 68, for example, as in the following equation.

Offset value = (value of second memory) ÷ 5 Further, in step 69, the control unit 1 calculates the difference between the value read from the output of the AD converter 9 and the value of the second memory 11, that is, ｛( The output of the AD converter 9) − (the value of the second memory 11)｝ is calculated, and the offset value and the absolute value of the difference are compared in step 70. If the offset value is larger in step 70, the process proceeds to step 74. If the offset value is smaller, the process proceeds to step 71 on the assumption that a clear change has occurred. In step 71, the controller 1 checks whether the difference is positive or negative. If the difference is negative, the controller 1 determines that the line closing voltage has decreased, and proceeds to step 72 to determine that the line terminal attached to the terminal is off-hook. If the difference is positive, it is considered that the line closing voltage has risen, and the routine proceeds to step 73, where it is determined that the attached line terminal is on-hook. Then, in step 74, the value of the first memory 10 is written to the second memory 11, and the process ends.

As described above, according to the fourth embodiment, since the offset value is set based on the value when the line closing voltage is in a stable state, a large voltage change occurs when the line closing voltage is high. Then, it is regarded that there has been a change in the attached terminal, and from a state where the line closing voltage is low, it can be regarded that there has been a change in the attached terminal even with a small voltage change, and there is an advantage that a more accurate determination can be made. If the change in the line voltage is smaller than the offset value, the change is regarded as not the change information of the co-located terminal. Therefore, even when the line closing voltage changes gradually or continuously, such as a change with time, an error occurs. It has the advantage of not judging.

(Embodiment 5) Next, a fifth embodiment of the operation of the apparatus having the configuration shown in FIG. 1 will be described with reference to FIG.

FIG. 8A is a flowchart of the main part showing the flow of the operation in the fifth embodiment, which replaces FIG. 4 of the first embodiment. FIG. 8B shows the data configuration of the determination table 17 shown in FIG. In the fifth embodiment, the control unit 1 compares the output of the AD converter 9 read in step 44 of FIG. 3 with the value stored in the first memory 10 in step 75. If they are different, the process from step 47 in FIG. 4 is performed. If the values compared in step 75 match, the control unit 1 checks the value of the first timer 13 in step 76. If the value of the first timer 13 has exceeded the predetermined value, the control unit 1 determines in step 77 that the read AD converter 9
Of the output value of the second memory 11 and the value of the
7 is output as an address. Then, in step 78, the data from the determination table 17 is read. For example, if the output value of the AD converter 9 is 3 and the value of the second memory 11 is 5, the control unit 1 reads data "1" from FIG. The control unit 1 stores the read data in step 79
In the case of "0", it is determined that there is no change in the line closing voltage, and the process proceeds to step 82; Rises to step 81, respectively. In step 80, it is determined that the attached line terminal is off-hook, and in step 81, it is determined that the attached line terminal is on-hook. And step 82
Then, the value of the first memory 10 is written to the second memory 11, and the process is terminated.

As described above, according to the fifth embodiment, by setting the data of the determination table 17 so that the area of “0” becomes larger as the value of the second memory becomes larger, the line closing is performed. From the state where the connection voltage is high, it is considered that there is a change in the attached terminal when the voltage changes greatly, and from the state where the line closing voltage is low, it is considered that there has been a change in the attached terminal even with a small voltage change, and more accurate It has the advantage of being able to judge. When the change in the line voltage is small, it is considered that the information is not the change information of the attached terminal by reading the data “0”, so that the line closing voltage gradually and continuously changes like a change over time. It has the advantage of not misjudging even at times. Further, by using the determination table 17, there is an advantage that the determination of the change of the attached terminal can be made immediately based on the data from the determination table without calculating the difference between the line closing voltages before and after the change and the offset value.

(Embodiment 6) A sixth embodiment of the operation of the apparatus having the configuration shown in FIG. 1 will be described with reference to FIG.

FIG. 9 is a flow chart of a main part showing the flow of the operation in the sixth embodiment.
Is a replacement for In the sixth embodiment,
The controller 1 reads the output value of the AD converter 9 in step 83, and checks in step 84 whether the read value is larger than a predetermined value. If it is larger, the second timer 14 is cleared and started in step 85, and the process proceeds to step 88. If smaller, the second in step 86
The value of the timer 14 is checked, and if the predetermined time has elapsed, it is determined in step 87 that the line power is off, and the flow proceeds to step 88.

According to the sixth embodiment, when the line closing voltage becomes smaller than a predetermined value for a certain period of time,
Since it is determined that the line power supply is in the disconnected state, the line closing operation can be terminated based on this determination as a state in which communication is impossible. If the automatic answering machine has an answering machine function, during the automatic answering, the second
By setting the determination value for the timer 14 to about 8 mSec, it is possible to treat it as a call termination determination and terminate the operation.

[0037]

As apparent from the above embodiment, the present invention has the following effects.

(1) A line closing voltage is input through an AD converter, and the first memory and the first timer determine that the input value is stable, and then store the input value in the second memory. When the voltage changes, the rise and fall of the line closing voltage are detected by comparing with the value stored in the second memory. Can be determined to have gone off-hook.

(2) By using the third memory and the counter,
By averaging the output of the AD converter, the AC component in the line closing voltage is removed, so that an accurate operation for determining a change in line state can be performed using only the DC component.

(3) When the change in the output value of the AD converter is small, it is determined that there is no change, so that it is possible to prevent unnecessary response to a slight change in the line closing voltage.

(4) By setting the data in the judgment table, it is possible to immediately judge the change of the attached terminal from the data from the judgment table without calculating the difference between the line closing voltages and the offset value before and after the change. Has an effect.

(5) When the line closing voltage becomes lower than a predetermined value for a certain period of time or longer, it is determined that the line power is in a cut-off state. The line closing operation can be ended.

(6) Even when the line closing voltage becomes higher than the input allowable voltage of the AD converter, the input voltage value is suppressed by the voltage dividing circuit, so that the AD converter can operate normally.

(7) It is possible to prevent the user from seeing the voltage change during dial transmission, and immediately start monitoring the line closing voltage change after dialing is completed.

(8) When a line terminal attached is off-hook, a confidential alarm is output to the caller, so that the possibility of eavesdropping or the like can be notified.

(9) An unnatural state in which the hold tone and the confidential talk alarm operate simultaneously can be eliminated.

(10) By adding a means for stopping the confidential alarm during the confidential alarm output, a three-party communication state can be formed according to the operator's need.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of a telephone device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an entire operation flow according to the first embodiment of the present invention;

FIG. 3 is a flowchart showing a flow of a line monitoring operation in the first embodiment;

FIG. 4 is a flowchart showing a flow of a line state determination operation in the first embodiment;

FIG. 5 is a flowchart showing an operation flow according to the second embodiment of the present invention;

FIG. 6 is a flowchart showing an operation flow in a third embodiment of the present invention.

FIG. 7 is a flowchart showing a flow of operation according to a fourth embodiment of the present invention.

FIG. 8A is a flowchart illustrating an operation flow according to a fifth embodiment of the present invention; FIG. 8B is a diagram illustrating a data configuration of a determination table according to the fifth embodiment of the present invention;

FIG. 9 is a flowchart showing a flow of an operation in a sixth embodiment of the present invention.

FIG. 10 is a circuit diagram of a line voltage monitoring circuit of a conventional telephone device.

FIG. 11 is a circuit diagram of a circuit for monitoring the state of a line terminal attached to a conventional telephone device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control part 2 Line connection terminal 3 Line closing circuit 5 Handset 6 Hold sound generation circuit 7 Secret talk alarm generation circuit 8 Voltage dividing circuit 9 AD converter 10 1st memory 11 2nd memory 12 3rd memory 13 1st Timer 14 second timer 15 hold button 16 alarm stop button 17 judgment table 18 hook switch 19 dial operation button 20 dial transmission circuit 21 counter

Claims (10)

(57) [Claims] An A / D converter for inputting a line voltage while the line is closed, converting the output to a digital value, a first storage means for temporarily storing an output value of the A / D converter, and an output of the A / D converter A first clear start is performed when the value is different from the value stored in the first storage means.
A second storage means for storing the output value of the A / D converter which does not change for a certain time when the output value of the A / D converter does not change for a certain time; and a value of the second storage means when the line is closed. And a means for comparing the output value of the AD converter with the value of the second storage means for a predetermined time after the value is stored in the second storage means. 2. An image processing apparatus comprising: a third storage means for reading a plurality of times while adding the output value of the AD converter to the third storage means to calculate an average value; The telephone device according to claim 1, wherein 3. The method according to claim 1, wherein the first storage means or the second storage means stores the information.
Compare the memorized value with the output value of the AD converter,
Change if the difference between the values is smaller than the offset value
It is characterized by having an offset judging means to judge that there is no
The telephone device according to claim 1, wherein 4. The telephone device according to claim 1, further comprising a judgment table for comparing the value of the second storage means with the output value of the AD converter. 5. When the output value of the A / D converter becomes smaller than a predetermined value for a certain period of time after the value is stored in the second storage means, the value is stored in the second storage means. 2. The telephone device according to claim 1, wherein it is determined that the line power supply is momentarily interrupted. 6. The telephone device according to claim 1, further comprising a voltage dividing means for inputting a line voltage to an AD converter via said voltage dividing means. 7. The telephone according to claim 1, further comprising a dial operation button and a dial transmitting means, wherein the output of the AD converter is not read during the operation of the dial transmitting means, and the first time measuring means is cleared and started. apparatus. 8. A confidential alarm generation means, a means for monitoring a change in the circuit closing voltage, and, when the circuit closing voltage drops sharply, activating the confidential alarm generating means to rapidly increase the circuit closing voltage. A telephone device that stops the above-mentioned confidential alarm generation means when it rises. 9. A hold button for instructing a line hold state during a call, a hold sound generating means, and operation of the hold button drives the hold sound generating means and inhibits the output of the confidential alarm generating means. The telephone device according to claim 8. 10. The telephone device according to claim 8, further comprising an alarm stop button, wherein said alarm stop button is depressed during output of the privacy alarm to stop said secret alarm generation means.