JPH04307845A - telephone equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telephone device that performs hold release and confidential message alarm operations when a telephone line terminal is connected to another line terminal.

0002

2. Description of the Related Art Conventionally, in this type of telephone device, the line voltage applied to the telephone device when the line of one telephone device is closed is stored in a capacitor, and the attached line terminal is used to off-hook the other telephone device. The configuration is such that a sudden change in line voltage that occurs when the line is closed is detected, or another line terminal is connected via one of the above-mentioned telephone devices.

[0003] Below, the main parts of a conventional telephone device of this type and the configuration of the connection between the telephone device and the line are shown in FIGS. 10 and 1.
1 will be explained.

FIG. 10 shows a first conventional example. In FIG. 10, 101 is a telephone device A, and 102 is a telephone device B. Even if the telephone device B 102 has the same circuit configuration as the telephone device A 101, it is a telephone device with a simple configuration, such as a 600-type telephone, for example. There may be. 103 is a line. Inside the telephone device, 104 is a positive side and 105 is a negative side. Reference numeral 106 denotes a group of diodes, which act so that no matter which polarity the telephone device A 101 is connected to the line 103, the positive side 104 always becomes positive and the negative side always becomes negative. 107 and 108 are resistances,
109 is a diode, 110 is a transistor, 111 is a control circuit, and 112 is a capacitor. 113 is a reservation circuit, which is driven by the control circuit 111;

Next, the operation of this conventional example will be explained. In FIG. 10, while the line is closed, the current supplied from the line 103 is input to the base of the transistor 110 via the diode group 106, resistor 107, diode 109, and resistor 108, so the transistor 110 is turned on. “L” level is input to the control circuit 111. Here, when the line connection voltage suddenly decreases, the electric charge charged in the capacitor 112 is discharged through the resistor 107, and the transistor 110 is momentarily turned off, and an "H" level is input to the control circuit 111. be done. The control circuit 111 receives “H” from the transistor 110.
When input, it is determined that the attached line terminal is off-hook, and the hold circuit 113 is driven to release the hold.

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

Next, the operation of this conventional example will be explained. When the telephone device B 102 connected to the attached line 120 goes off-hook, that is, when the attached 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
turns on, and the “H” level is input to the control circuit 111 by the inverter 119. The control circuit 111 determines that the attached line terminal is on-hook when the output of the phototransistor 118 is "L", and that it is off-hook when the output is "H".

In this way, the second conventional example has the same effect as the first conventional example.

[0009]

[Problems to be Solved by the Invention] However, in the above-mentioned conventional telephone device, in the first conventional example shown in FIG. It was reacting to the voltage drop inside. Furthermore, it was not possible to detect an increase in line voltage. Therefore, since the control circuit 111 operates only under extremely limited line conditions such as low line resistance, it cannot detect the transition of the attached line terminal to off-hook, and therefore cannot perform hold release or confidential conversation alarm functions. I couldn't make it happen.

In the second conventional example shown in FIG. 11, a photocoupler is inserted in series with the line terminal installed, so the voltage drop due to the resistance of the line and the forward voltage of the LED are added. There was a problem in that not only the voltage supplied to the line terminal installed in the line decreased, which had an adverse effect, but also that other line terminal devices could not be connected without going through the telephone device C114.

[0011] The present invention solves these conventional problems, and can detect off-hook and on-hook without affecting the attached line terminal, and can detect when an attached terminal device interrupts a call. It is an object of the present invention to provide an excellent telephone device that can reliably release a call from hold and generate a confidential call alarm sound.

0012

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a first means that includes an AD converter and an AD converter.
A means for storing the output value of the converter in two stages using first and second storage means, a first timer means, and an initial setting means are provided, and a change in line connection voltage is detected and the change is detected. This system is designed to determine whether the line terminal attached to the base is off-hook or on-hook. The second means further includes a third means.
The output of the AD converter is read a plurality of times and the average value thereof is replaced with the line connection voltage. The third means is to provide an offset determination means for reading the AD converter output so as not to react to subtle changes. The fourth means is to provide a judgment table, and to judge the validity of the change based on the data of the judgment table, which is addressed by the values before and after the change in the line connection voltage. A fifth means is to provide a second timer means to detect when the line connection voltage continuously falls below a certain value. A sixth means is to provide a voltage dividing means at the input of the AD converter to prevent a voltage exceeding a certain level from being input to the AD converter. The seventh means is such that the output of the AD converter is not read as an invalid value while the dial transmission circuit is in operation, and furthermore, the first clock means is cleared and started. In addition, in order to achieve another object, the eighth means includes a means for detecting a change in line connection voltage and a means for outputting a confidential message alarm, and outputs a confidential message alarm based on the determination of the detection means. It is something. 9th
The means is provided with a hold button and a hold tone generating means, and when the hold button is operated, that is, when the line is placed on hold, the confidential message alarm output is stopped, and the confidential message alarm is not output while the line is on hold. It is. A tenth means is to provide an alarm stop button, and when the button is pressed while the confidential message alarm is being output, the confidential message alarm output is stopped.

[0013]

[Operation] The present invention has the following effects due to the above-described structure. The first means inputs the line connection voltage via the AD converter, and after determining that the input value is stabilized by the first storage means and the first timer, the input value is stored in the second storage means; When the line connection voltage changes, a rise or fall in the line connection voltage is detected by comparing it with the value stored in the second storage means, and when the line connection voltage increases, the attached terminal device goes on-hook, When it drops, it can be determined that it has gone off the hook. By averaging the output of the AD converter using the second means and the third storage means and the counter, the alternating current component in the line closing voltage is removed, so that accurate determination of line state changes can be made using only the direct current component. can perform actions. With the third means, by determining that there is no change when the change in the output value of the AD converter is small, it is possible to prevent unnecessary reactions to slight changes in the line connection 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 assumed that there has been a change in the attached terminal when there is a large voltage change, and the line is closed. When the voltage is low, even a small voltage change can be considered as a change in the attached terminal.
More accurate judgment is also possible. In this case, if the change in line voltage is smaller than the above offset value, this is not considered to be change information for the attached terminal, so if the line connection voltage changes gradually or continuously, such as over time, But don't misjudge. By the fourth means, the same effect as the third means can be obtained by setting the data in the judgment table, and the difference in line connection voltage before and after the change or the offset value can be calculated without calculating the difference or offset value. This has the effect that it is possible to immediately judge changes in the attached terminal based on the data. The fifth means determines that the line power is disconnected when the line closing voltage becomes lower than a predetermined value for a certain period of time, and based on this determination, it is determined that the line is in a state where calls are not possible. The line closing operation can be completed. The sixth means allows the AD converter to operate normally even when the line connection voltage is higher than the allowable input voltage of the AD converter. The seventh means prevents viewing of voltage changes during dialing, and allows monitoring of line connection voltage changes to be started immediately after dialing is completed. According to the eighth means, by outputting a confidential message alarm to the caller, it is possible to notify that the attached line terminal is off-hook and there is a possibility of eavesdropping, etc. By the ninth means,
It is possible to eliminate an unnatural state in which the hold music and secret message alarm operate at the same time. According to the tenth means, by pressing this button while the confidential message alarm is being output, the confidential message alarm can be stopped and a three-way communication state can be established.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 section which is constituted by a microcomputer and controls the entire apparatus. 2 is a line connection terminal. 3 is a line closing circuit, which is driven by the control section 1; 4 is a speech network; 5 is a handset consisting of a receiver and a microphone;
6 is a hold tone generation circuit, and 7 is a secret alarm generation circuit. The hold tone generation circuit 6 and the confidential talk alarm generation circuit 7 are driven by the control section 1 and output to the speech network 4. 8 is a voltage dividing circuit, which divides the line connection voltage. 9 is A
It is a D converter, which receives the line connection 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; 13
, 14 are first and second timers, 15 is a hold button, 16 is an alarm stop button, 17 is a determination table, 18
is a hook switch, 19 is a dial operation button,
The dial data is sent to the control section 1. 20 is a dial transmission circuit, and this dial transmission circuit 20 is connected to the control unit 1.
When the dialing data is input from the line, the line is dialed and whether or not dialing is in progress is always outputted to the control section 1. 21 is a counter. The output terminal of the control unit 1 includes a line closing circuit 3, a speech network 4, a hold tone generation circuit 6, a secret alarm generation circuit 7, and a first memory 10.
, a second memory 11, a third memory 12, a first timer 13, a second timer 14, a determination table 17, a dialing circuit 20, and a counter 21 are connected. In addition, the input terminals of the control unit 1 include a hold button 15, an alarm stop button 16, a hook switch 18, and a dial operation button 1.
9, as well as AD converter 9, first memory 10, second memory 11, third memory 12, and first timer 13
, the second timer 14, the determination table 17, the dial transmission circuit 20, and the counter 21.

Next, a concrete example will be explained. (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. 2 is a flowchart showing the overall 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. 2. FIG. 4 is a flowchart showing details of the line state determination operation among the steps included in FIG. 2.

In FIG. 2, in the initial state, the control section 1 monitors the state of the hook switch 18 in step 22. When the handset 5 is picked up at this point, it becomes an off-hook state, and the control section 1 drives the line closing circuit 3 in step 23 to close the line. This allows the line to connect to line connection terminal 2.
and the speech network 4 via the line connection circuit 3.
At the same time as power is supplied for telephone calls to the voltage dividing circuit 8, a line closing voltage is input to the voltage dividing circuit 8. Further, in step 24, the control section 1 clears the counter 21 and the three memories 10, 11, and 12, and shifts to a talking state. In the call state, the control unit 1 monitors the hold button 15, alarm stop button 16, and dial operation button 19 in step 25, monitors changes in line status in step 29, and monitors changes in the status of the hook switch 18 in step 33. ing. Here, when the control unit 1 determines in step 30 that the attached line terminal has gone off-hook due to a drop in the line connection voltage, it drives the confidential talk alarm generation circuit 7 in step 31 to output a confidential talk alarm sound. Further, when the control unit 1 determines that the attached line terminal is on-hook due to an increase in the line connection voltage in step 30, it stops driving the confidential talk alarm generation circuit 7 in step 32, and stops outputting the confidential talk alarm sound. make it stop. When the control unit 1 determines that the dial operation button 19 has been pressed in step 26 during a call, the process proceeds to step 27.
The dial data is output to the dial transmission circuit 20. In the call state, the control unit 1 presses the hold button 15 in step 26.
If it is determined that the key has been pressed, the private conversation alarm generation circuit 7 is deactivated in step 36, the hold tone generation circuit 6 is activated to output a hold tone in step 37, and the line is put on hold. In the line hold state, the control unit 1 performs step 38.
At step 40, changes in the state of the line are monitored, and at step 40, changes in the state of the hook switch 18 are monitored. Here, control section 1
If it is determined in step 39 that the attached line terminal has gone off-hook due to a drop in the line connection voltage, the process proceeds to step 4.
At step 1, the drive of the hold tone generation circuit 6 is released to stop the hold tone and release the line hold state.

The details of the line state change monitoring operation shown in steps 29 and 38 in FIG. 2 will now be explained using FIG. 3. The control unit 1 reads the state of the dialing circuit 20 in step 42, and if dialing is in progress, clears and starts the first timer 13 in step 43. If dialing is not in progress, step 44
Read the output value of the AD converter 9 in step 45.
A change in line status is determined by .

The details of the line state change determination operation shown in step 45 in FIG. 2 will now be described with reference to FIG. 4. In step 46, the control unit 1 compares the read output value of the AD converter 9 and the value in 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 to the first memory 10 in step 48. If the values compared in step 46 match, the control unit 1 controls the first timer 1 in step 49.
Check the value of 3. If the value of the first timer 13 exceeds the predetermined value, the controller 1 controls the second timer 13 in step 50.
The value in the memory 11 is checked, and if it is cleared, the process moves to step 54. If it is not cleared, the read output value of the AD converter 9 and the second memory 11
Compare with the value of . At this time, if the output value of the AD converter 9 is larger, the control unit 1 determines that the attached line terminal is on-hook in step 53, and if the value of the second memory 11 is larger, the control unit 1 is step 52
It is determined that the attached line terminal has gone off-hook. Furthermore, in step 54, the value of the first memory 10 is written to the second memory 11, and the process is ended.

As described above, according to the first embodiment, A
The line closing voltage is input through the D converter 9, and after the input value becomes stable, it is stored in the second memory 11, and when the line closing voltage changes, the value stored in the second memory 11 is changed. This has the advantage of being able to detect increases and decreases in the line connection voltage and determine whether the attached terminal device is on-hook or off-hook. Also,
Based on this determination, a confidential message alarm is output to the caller, thereby having the effect of notifying that the attached line terminal is off-hook and there is a possibility of eavesdropping, etc. Also,
When the hold button 15 is pressed, the operation of the confidential message alarm generating means 7 is released and the confidential message alarm operation is prohibited during the hold, thereby eliminating the unnaturalness that the hold tone and confidential message alarm operate at the same time. can. In addition, the alarm stop button 16
It has the advantage that if this button is pressed while the confidential message alarm is being output, the private conversation alarm generation circuit 7 can be deactivated, thereby creating a three-way communication state. In addition, by compressing the line closing voltage to within the allowable input voltage range of the AD converter 9 and inputting it via the voltage dividing circuit 8, even if the line closing voltage is higher than the allowable input voltage of the AD converter 9, the AD This has the advantage that the converter 9 can be operated normally. In addition, by not reading the output of the AD converter 9 during dialing, and by clearing and starting the first timer 13, it does not react to changes in the line connection voltage during dialing, and from the time the dialing ends. This has the advantage that detection can be started anew.

(Embodiment 2) Next, 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 flowchart showing the main part of the operation in the second embodiment, and is similar to FIG. 3 in the first embodiment.
It replaces. 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 it into the third memory 12 as it is. Further, in step 57, the counter 21 is incremented,
In step 58, the value of the counter 21 is checked, and if it is less than the set value, the line state change monitoring process is ended. 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.
Replaced with the output value of the D converter 9 and stored in 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
(see).

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 alternating current component in the line connection voltage is removed. Therefore, it has the advantage of being able to accurately determine changes in line conditions 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 using FIG. 6.

FIG. 6 is a flowchart showing the main part of the operation in the third embodiment, and is similar to FIG. 4 of the first embodiment.
It replaces. 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 above-mentioned calculated value with the first offset value, and if the above-mentioned offset value is larger,
The read output of the AD converter 9 and the first memory 10
It is assumed that the values of are the same, and the processing from step 49 onward in FIG. 4 is performed. In step 64, if the offset value is smaller, it is assumed that the read output of the AD converter 9 and the value in the first memory 10 are different, and as shown in FIG.
The processing from step 47 onwards is performed.

According to the third embodiment, step 63
, 64 constitute an offset determination means, and A
If the change in the output value of the D converter 9 is small, it is determined that there is no change, which has the advantage of preventing unnecessary reactions to slight changes in the line connection voltage.

(Embodiment 4) Next, a fourth embodiment of the operation of the apparatus having the configuration shown in FIG. 1 will be described using FIG. 7.

FIG. 7 is a flowchart showing the main part of the operation in the fourth embodiment, and is similar to FIG. 4 of the first embodiment.
It replaces. 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 processes from step 47 onward in FIG. 4 are 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 exceeds the predetermined value, the control unit 1 checks the value of the second memory 11 in step 67, and if it is cleared, the process moves to step 74. If it is not cleared,
In step 68, the control unit 1 calculates an offset value from the value in the second memory 11, for example, as shown in the following equation.

Offset value = (value of second memory) ÷ 5
Further, in step 69, the control unit 1 calculates the difference between the read output of the AD converter 9 and the value of the second memory 11, that is, {(output of the AD converter 9) - (value of the second memory 11) } is calculated, and in step 70, the offset value and the absolute value of the difference are compared. If the offset value is larger in step 70, the process moves to step 74; if it is smaller, it is assumed that there has been a clear change, and the process moves to step 71. In step 71, the control unit 1 checks whether the difference is positive or negative, and if the difference is negative, it considers that the line connection voltage has decreased, and proceeds to step 72, where it determines that the attached line terminal has gone off-hook. If the difference is positive, it is assumed that the line connection voltage has increased, and the process 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 connection voltage is in a stable state, the voltage does not change significantly from a state where the line connection voltage is high. It is assumed that there has been a change in the attached terminal when the line connection voltage is low, and even a small voltage change can be considered as a change in the attached terminal when the line connection voltage is low, which has the advantage of allowing more accurate judgment. Furthermore, if the change in line voltage is smaller than the above offset value, this is considered not to be change information for the attached terminal, so even if the line connection voltage changes gradually or continuously, such as over time, it will cause an error. It has the advantage of not being judgmental.

(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. 8(A) is a flowchart showing the main part of the operation in the fifth embodiment, and replaces FIG. 4 of the first embodiment. FIG. 8(B) shows the data structure 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 processes from step 47 onward in FIG. 4 are 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 exceeds the predetermined value, in step 77, the control unit 1 controls the read AD converter 9
The output value of and the value of the second memory 11 are determined by
Outputs the address to 7. Then, in step 78, 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, data "1" is read into the control unit 1 from FIG. The control unit 1 transfers the read data to step 79.
If it is "0", it is assumed that there is no change in the line closing voltage and the process goes to step 82; if it is "1", it is assumed that the line closing voltage has decreased and the process goes to step 80; if it is "2", the line closing voltage is checked. Assuming that the value has increased, the process moves to step 81, respectively. In step 80, it is determined that the line terminal installed in parallel is off-hook, and in step 81, it is determined that the line terminal installed in parallel is placed on hook. and step 82
Then, the value of the first memory 10 is written to the second memory 11, and the process ends.

As described above, according to the fifth embodiment, the data in the determination table 17 is set such that the larger the value in the second memory, the wider the area of "0", so that the line is closed. If the line connection voltage is high, a large voltage change can be considered as a change in the attached terminal, and if the line connection voltage is low, even a small voltage change can be considered as a change in the attached terminal, making it more accurate. Has the advantage of being able to make decisions. In addition, if the change in line voltage is small, "0" data is read and it is assumed that it is not change information on the attached terminal, so the line connection voltage may change gradually or continuously, such as over time. This has the advantage of not erroneously making a judgment even at times. Furthermore, by using the determination table 17, there is an advantage that a change in the attached terminal can be immediately determined based on the data from the determination table, without having to calculate the difference in line connection voltage before and after the change or the offset value.

(Embodiment 6) Next, 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 flowchart showing the main part of the operation in the sixth embodiment, and is similar to FIG. 3 of the first embodiment.
It replaces. In the sixth embodiment above,
The control unit 1 reads the output value of the AD converter 9 in step 83, and checks in step 84 whether or not 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 moves to step 88. If it is smaller, the second
The value of the timer 14 is checked, and if a certain period of time has elapsed, it is determined in step 87 that the line power is in a disconnected state, and the process proceeds to step 88.

According to the sixth embodiment, when the line connection voltage becomes smaller than the predetermined value for a certain period of time,
Since it is determined that the line power supply is in a disconnected state, based on this determination, it is possible to terminate the line closing operation as a state in which a call is not possible. In addition, if the automatic response answering function is provided, during automatic response, the second
By setting the determination value for the timer 14 to about 8 mSec, it is possible to treat this as a determination that the caller's call is over and terminate the operation.

[0037]

Effects of the Invention As is clear from the above embodiments, the present invention has the following effects.

(1) Input the line closing voltage through the AD converter, and after determining that the input value is stable by the first memory and first timer, store it in the second memory, and then close the line. By comparing the voltage change with the value stored in the second memory, a rise or fall in the line connection voltage is detected, and when the voltage rises, the attached terminal device goes on-hook, and when it falls, the line connection voltage goes on-hook. can be determined to have gone off the hook.

(2) By the third memory and counter,
By averaging the output of the AD converter, the alternating current component in the line connection voltage is removed, so it is possible to accurately determine a change in the line state using only the direct current component.

(3) By determining that there is no change when the change in the output value of the AD converter is small, it is possible to prevent unnecessary reactions to slight changes in the line connection voltage.

(4) By setting the data in the judgment table, it is possible to immediately judge changes in attached terminals using the data from the judgment table without having to calculate the difference in line connection voltage before and after the change or the offset value. have an effect.

(5) When the line closing voltage becomes lower than a predetermined value for a certain period of time, it is determined that the line power is disconnected, and based on this determination, the state is determined to be in a state where calls are not possible. The line closing operation can be completed.

(6) Even if the line connection voltage becomes higher than the allowable input 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 voltage changes from being seen during dialing, and to immediately start monitoring line connection voltage changes after dialing is completed.

(8) When the attached line terminal goes off-hook, it is possible to notify the caller of the possibility of eavesdropping by outputting a confidential message alarm to the caller.

(9) It is possible to eliminate an unnatural situation in which the hold tone and confidential message alarm operate at the same time.

(10) By adding means for stopping the confidential conversation alarm while the confidential conversation alarm is being output, a three-party conversation state can be formed according to the operator's needs.

[Brief explanation of 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 the overall flow of operations in the first embodiment of the present invention.

[Fig. 3] Flowchart showing the flow of line monitoring operations in the first embodiment.

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

FIG. 5 is a flowchart showing the flow of operations in the second embodiment of the present invention.

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

FIG. 7 is a flowchart showing the flow of operations in the fourth embodiment of the present invention.

FIG. 8 (A) Flowchart showing the flow of operations in the fifth embodiment of the present invention; (B) Diagram showing the data structure of the determination table in the fifth embodiment of the present invention;

FIG. 9 is a flowchart showing the flow of operations in the 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 status of a line terminal attached to a conventional telephone device.

[Explanation of symbols]

1 Control section 2 Line connection terminal 3 Line closing circuit 5　Handset 6 Hold tone generation circuit 7 Confidential alarm generation circuit 8 Voltage divider circuit 9 AD converter 10 First memory 11 Second memory 12 Third memory 13 First 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)

[Claims] 1. An AD converter that inputs a line voltage during line connection, converts it into a digital value, and outputs it, a first storage means that temporarily stores an output value of the AD converter, and an output of the AD converter. The 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 an output value of the AD converter that does not change for a certain period of time when the output value of the AD converter does not change for a certain period of time; and a value of the second storage device when the line is closed. and a telephone device that compares the output value of the AD converter and the value of the second storage means for a certain period of time after the value is stored in the second storage means. 2. A third storage means, wherein the output value of the AD converter is added to the third storage means and read a plurality of times to calculate an average value, and the average value is used as the output value of the AD converter. 2. The telephone device according to claim 1, wherein the telephone device is replaced with: 3. The telephone device according to claim 1, having an offset determination function. 4. The telephone device according to claim 1, further comprising a determination table for comparing the value of the second storage means and the output value of the AD converter. 5. A second clock means, wherein after the value is stored in the second storage means, when the output value of the AD converter continues to be smaller than a predetermined value for a certain period of time, 2. The telephone device according to claim 1, wherein the telephone device determines that there is a momentary power outage in the line power supply. 6. The telephone device according to claim 1, further comprising voltage dividing means for inputting the line voltage to the AD converter via the voltage dividing means. 7. The telephone according to claim 1, further comprising a dial operation button and a dialing means, wherein the output of the AD converter is not read while the dialing means is in operation, and the first time measuring means is cleared to start. Device. 8. A means for generating a confidential message alarm, a means for monitoring changes in a line closing voltage, and a means for activating the confidential message alarm generating means when the line closing voltage suddenly decreases. A telephone device that stops the secret message alarm generating means when the alarm rises. 9. A hold button for instructing a line hold state during a call, a hold tone generating means, and an operation of the hold button to drive the hold tone generating means and prohibit output of the confidential conversation 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 pressing the alarm stop button while the secret message alarm is being output stops the secret message alarm generating means.