JPS5835437B2 - Confidential control method for button telephone equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a confidential communication control system for a button telephone device that connects a key telephone and a main device with a three-pair line.

Key telephones have been put into practical use with features such as mutual calling between extensions and ease of handling.

There are two types of button telephones: a so-called multi-wire type and an electronic type using three pairs of wires, which improves the disadvantage of the multi-wire type in that it requires a large number of wires.

This electronic key telephone device connects the main device and each key telephone device with three pairs of lines, so that control signals can be multiplexed and transmitted.

However, by introducing the multiplexing technology, this button telephone device requires a complicated control circuit, especially inside the main device, and the button telephone device as a whole tends to become complicated and expensive.

The present invention has been made in consideration of the fact that multiplexed key telephone devices are complicated and expensive as described above.In particular, the present invention simplifies the secret control circuit portion related to the control of call cross points of central office lines and extension lines. The present invention provides a secret control method for a button weight device that is designed to be more flexible.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is for explaining the present invention, and for the sake of clarity, the handset side and the calling speaker side of the button telephone are separated, and the terminal circuit in the main device is also divided into the calling path side and the calling voice transmission path side. It is shown separately.

To explain the configuration, 1 and 2 are central lines, and these central lines 1 and 2 are:
It is connected to a call crosspoint 5 via central line circuits 3 and 4.

An extension circuit 6 is connected to this call cross point 5,
This extension circuit 6 is further connected to a paging crosspoint 8 via an extension paging circuit 7.

A central office line paging circuit 9 is connected to this paging crosspoint 8 .

The telephone cross point 5 includes the office line circuits 3, 4,
A terminal circuit 10A selectively connected to the extension circuit 6.

Transceivers 13, 14, and 15 are connected via 11A and 12A.

On the other hand, the calling cross point 8 has terminal circuits 10B and 1 selectively connected to the office line calling circuit 9 and the extension calling circuit 7.
Call speakers 16, 17.1 via 1B, 12B
8 is connected.

Furthermore, the handset 13, 14, 15 and the calling speaker 16, 17,
18 constitutes each button telephone 19, 20, 21, and the other part 22 is the main device.

and the handset 13 of each button telephone 19, 20, 21,
14, 15 and the main device 22 are connected by a speech tone transmission path 23,
24, 25, and call speakers 10, 16,
17.degree. 18 and the main device 22 are connected by a calling voice transmission path 26.degree. 27.28.

Also 19S and 20S. 218, each button telephone 19,
20.21 button switch, 29, 30.31
is an upstream control signal transmission line that transmits signals generated by operating the button switches 19S, 208, and 218.

In addition, 32, 33, 34 are each button telephone 19.20
, 21 are display elements such as display lamps, and these display elements 32, 33, 34 are connected to downlink control signal transmission lines 35, 36,
It is configured to be controlled by a downlink control signal transmitted at 37.

Further, a common line 500 is connected to the office line circuits 3 and 4 and the extension line circuit 6, and this common line 500 is connected to a secret signal generation circuit 600.
The output terminal of 00 is connected to the voice call crosspoint 5.

To explain the operation in this configuration, first, in the case of a central office line call, when the button telephone 19 selects central office line 1 using the button switch 19S, the information of the selected button switch 198 passes up the control signal transmission line 29 to the terminal circuit. 10A to the call crosspoint 5 and control it, thereby connecting the handset 13 and the call voice transmission line 23.
, Point 5 of terminal circuit 10A1 call cross point 5
a Connected to the office line 1 via the office line circuit 3.

However, this operation only occurs when office line 1 is not being used by any other key telephone; if office line 1 is being used by another key telephone, office line circuit 3 is in the talking state. This is transmitted to the secret signal generation circuit 600 via the common line 500, so that the secret signal output cuff 0 that performs the secret operation regarding the central office line 1 is transmitted from this circuit 600 to the secret signal generation circuit 600.
0 is generated and this is added as a control signal for the call crosspoint 5.

As a result, even if the button switch 19S of the button telephone 19 is operated, the point 5a of the call cross point 5 is controlled not to be closed, resulting in a so-called confidential conversation state.

Next, in the case of an incoming call from a central office line, when an incoming signal is given from the central office line 2, the incoming call is detected in the central office line circuit 4, and a preset key telephone, for example, the key telephone 20, is When tone paging is performed, a ring tone is generated from the office line paging circuit 9, sent to the paging speaker 17 via the paging cross point 8 point 8a, the terminal circuit 11B1, paging audio transmission line 27, and the paging sound is sent from the speaker 17 to the paging speaker 17. A sound is generated.

This voice call is provided with a call crosspoint 5 and an independent call crosspoint 8, and the ringing tone is transmitted through a route different from the call path, so even if the key telephone 20 being called is in the middle of a call, can also make calls.

If the key telephone 20 answers here, the handset 14 is connected to the call voice transmission path 24, the terminal circuit 11A1, and the call cross point 5 at point 5b.

It is connected to the office line 2 via the office line circuit 4 and a response is made.

At this time, as for the previous station line call, the incoming call detection on the station line 2 disappears, so the call stops and the call cross point ha, 8a is restored.

Next, in the case of an extension call, for example, if the key telephone 19 makes a call, the handset 13 of this key telephone 19 is connected to the voice transmission line 23, the terminal circuit 10A1, the point 5c of the call cross point 5, the extension circuit 6, and the extension calling circuit. Connected to 7.

If you dial in this state, the called party will be selected.

In the case of MF dialing, this dialing signal can directly provide dialing to the extension calling circuit 9 through the communication path.

Alternatively, the dial signal can be transmitted as a control signal from the key telephone to the main unit through an uplink control signal transmission path, and then provided to the extension calling circuit 7.

Now, suppose that the called party is the button telephone 20 due to the dialing operation described above.

Here, if a voice call is to be made, the voice from the key telephone 19 is transmitted to the extension calling circuit 7 as described above, and then further to the point 8 of the call cross point 8.
The signal is sent to the calling speaker 17 via the b1 terminal circuit 11B1 calling voice communication path 27, and a voice calling is performed.

This extension voice call can also be made even if the called party's key telephone 20 is in use.

Note that although the above description is about voice calling, this is not limited to this, for example, if the route is disconnected in the extension calling circuit 7,
Tone calling can also be performed by sending a ringback tone to the calling party and a ringback tone to the called party.

In addition, in the above-mentioned voice call, by adding a hand-free response process that has the functions of a calling speaker and a microphone instead of the calling speaker 17 of the called party's key telephone 20, it is possible to receive a call from the calling party's key telephone 19. It is also possible to use the line up to the caller's button telephone 20 in both directions for calling and hands-free response.

Next, the case of an extension call will be explained.

It is assumed that an extension call is made as described above and that the call is answered.

Since it is possible to answer from any button telephone device in the button telephone device, here, for example, the button telephone 21
Let us now discuss the case in which the following responds.

That is, the handset 15 of the button telephone 21 is connected to the - call voice transmission line 25, the terminal circuit 12A1, the call cross point 5;
The caller's key telephone 19 is connected in parallel to the extension circuit 6 via the call cross point 5.

At this time, the calling of the extension is stopped, the connection between the extension circuit 6 and the extension calling circuit 7 is cut off, and the point 8b of the calling cross point 8 is restored.

In this way, calls between extension lines can be made.

Note that the display element 3 on each button telephone 19, 20, 21
2, 33, and 34 are transmitted to the terminal circuits 10B and 11B12B through a display signal control circuit (not shown),
Downlink control signal transmission lines 35, 3B.

37 to the display elements 32, 33, and 34 of the button telephones 19, 20, and 21, and each status J of the central office line and the interior is transmitted to the display elements 32, 33, and 34 of the key telephones 19, 20, and 21, and the signals are turned on or blinked at a predetermined period.

Next, the configuration of the confidential conversation control section will be explained with reference to FIG.

Each button telephone 19, 20. The handsets 13 and 14 (21 is omitted for convenience) are connected to the 3-pair voice transmission lines 23 and 24 via a transformer 4L42, and are connected to the transformer 43 and 44 of the main device 22 via this, and Button switch 19S, 20S for each button telephone 19°20
are connected to parallel-serial conversion circuits 45 and 46, and these parallel-serial conversion circuits 45 and 46 are connected to 3 through transformers 47 and 48.
It is connected to the pair of uplink control signal transmission lines 29 and 30, and is connected to the transformer 49 and 50 of the main device 22 via this.

On the other hand, within the main device 22, both ends of the windings on the crosspoint side of the transformers 43, 44 are connected to the communication crosspoint 5 via communication paths 51, 52.

This communication cross point 5 is a balanced cross point 551.
552,561.

562 is provided.

On the other hand, the upstream control signal detection circuit 57 is connected to the transformer 49.50.
．． 58 is connected, and the output terminal of this circuit 57.58 is connected to one input terminal of AND gate 59. connected to.

The other input terminals of the AND gates 59 and 60 are connected to the output terminal of the secret signal generation circuit 600, and the output terminals are connected to one input terminal of the AND gates 631.632 and 641.642. AND gate 631°632.64
Each output end of 1.642 is connected to the balanced cross point 55.
1.552.561.562, and the other input terminal is connected to the timing pulse generation circuit 300.

Further, in the office line circuit 3, a transformer 100 located between the communication path 53 and the office line 1 is provided, and the midpoint of the winding of this transformer 100 on the communication path 53 side is grounded via a resistor 101, and It is connected to the call signal detection circuit 102.

The output terminal of this call signal detection circuit 102 is the line relay 1
03 and one input terminal of the AND gate 104.

The other input terminal of the AND gate 104 is connected to the timing signal generation circuit 300, and the output terminal is connected to the common line 500 and further connected to the secret signal generation circuit 600.

601 is a logic inverter.

The line h in the station line circuit 3 is a contact point of the line relay 103.

The operation in such a configuration will be explained.

First, a preliminary explanation will be given before explaining the specific operation of the circuit.

First, in a button telephone device, the length of the wiring between the button telephone and the main device is generally several hundred meters at most.

Therefore, in FIG. 2, the timing of the timing pulse generation circuit 300 of the main device 22 and the timing of each button telephone 19,
If the internal timing, such as 0.21, is adjusted by some method, and the period and width of the timing pulse are appropriate for the transmission path, the signal is multiplexed from the button telephone and passed through the uplink control signal transmission path. The uplink control signal transmitted to the main device can be considered to match the timing within the main device as it is.

However, in reality, measures such as using strobe pulses are also used to compensate for the delay.

Second, in this button telephone device, timings are assigned to each office line and each extension line.

That is, as shown in FIG.
2. . . . For Tn, timing T1 is assigned to station line 1, timing T2 is assigned to station line 2, and so on.

Therefore, in addition to the fact that the key telephone and the main device have the same timing as mentioned above, the uplink control signal from the key telephone is, for example, at the main device at the timing T.
1, it is determined that the button corresponding to station line 1 has been operated.

Moreover, the above timings are commonly used for all button telephones in the device.

Here, before explaining the specific operation, let us consider a situation where the key telephone 19 makes a call on the central office line 1.

In the button telephone 19, the off-hook operation closes the hook switch 19Sc.

Then, the hook switch signal multiplexed by the parallel-to-serial conversion circuit 45 is sent to the uplink control signal transmission line 29 via the transformer 47, and is transmitted to the transformer 4 on the main device 22 side.
9 is detected as a multiplexed pulse by the uplink control signal detection circuit 57, and further demodulated by the hook switch signal detection circuit 61.

Furthermore, the output of this detection 1 circuit 61 is guided from the middle point of the transformer 43 to the communication path 51 to a balanced cross point 55.
1,552.

Next, the button 19Sa corresponding to the central line 1 is operated.

Then, this time, button 198a and hook switch 19
The signal Sc is input to the parallel-serial conversion circuit 45, and its output (450 in FIG. 3) reaches the upstream control signal detection circuit 57 through the transformer 47, the upstream control signal transmission line 29, and the transformer 49, as before.

290 in FIG. 3 shows a waveform transmitted through the uplink control signal transmission path, and 570 in FIG. 3 shows the output of the uplink control signal detection circuit 57 at this time.

Here, in the hook switch signal detection circuit 61, since the hook switch 19Sc has remained closed since the time described above, and the hook switch signal is continuously applied, the output thereof is as shown in FIG. 3 610. As a result, a voltage is continuously applied to the balanced cross points 551 and 552.

On the other hand, the signal corresponding to the button 19sa is first applied to the AND gate 59.

The other input of this AND gate 59 is applied with the output 00 of the secret signal generation circuit 600 (the operation of this circuit will be explained later).

) Now, it is assumed that this confidential signal output cuff 00 is the signal 1 during the timing T1 corresponding to the central office line 1.

Then, the signal corresponding to the button 19-8a passes through the AND gate 59, and further passes through the AND gate 631.6.
There are 32 inputs.

Since the signal corresponding to the button 19Sa is a signal that occurs between the timing T1, the AND gate 631 performs an AND with the timing T1, thereby separating the signal from the button 198a, and 630 in FIG. produces an output like .

Then, by applying a trigger signal to the balanced cross point 551, the balanced cross point 551 is turned on.

As already mentioned, the hook switch signal detection circuit 6
1, the output is connected from the midpoint of the transformer 43 to the communication path 51.
Since a voltage is applied to the balanced cross points 551 and 552, the current flows from both ends of the transformer 43 to the balanced cross point 551, and then from both ends of the transformer 100 of the station line circuit 3 through the middle point and through the resistor 101. flows, a current flows through the balanced cross point 551, and the on state of this cross point 551 is maintained.

Therefore, there is no need for a button signal from now on.

Therefore, the buttons are non-locking buttons.

Further, in the office line circuit 3, since a voltage is generated in the resistor 101 by the current, this is detected by the call signal detection circuit 102 and the line relay 103 is operated.

Then, the handset 13 of the button telephone 19 is connected to the transformer 41.
, the telephone voice transmission line 23, the transformer 43, the cross point 551, the transformer 100, the line relay contact, and the central office line 1 through h.

Here, the station line 1 is maintained with the secondary side of the transformer 100 as a DC load.

In the office line circuit 3, the output of the call signal detection circuit 102 is also input to one input terminal of an AND gate 104.

The timing pulse T1 from the timing signal generation circuit 300 is applied to the other input of the AND gate 104.

The output of this AND gate'-NO4 has a wired-OR configuration and is output to the common line 500.

As a result, on the common line 500, the timing ゛T
1 and the common line 500 is signal 1, this indicates that the office line 1 is in communication.

The signal on this common line 500 is input to a secret signal generation circuit 600, and is outputted as a secret signal 700 through an internal logical NOT gate 601.

Figure 4 shows the output when all lines other than station line 1 are not used.
Shown as 00.

In this state, the button telephone 20 goes on-hook to connect to the central office line 1, and the button 20S corresponding to the central office line 1
When a is operated, the hook switch 20Sc is activated by on-hook in the call operation of the button telephone 19 to the central office line 1, as described above, and the hook switch signal is multiplexed by the parallel-to-serial conversion circuit 46, Through the transformer 48, the upstream control signal transmission line 30, the transformer 50, and the upstream control signal detection circuit 58, it is demodulated by the hook switch signal detection circuit 62, and the output voltage is guided from the midpoint of the transformer 44 to the communication line 52, and is connected to a balanced cross point. 561.562.

Furthermore, the button 20Sa corresponding to the central office line 1 is operated.

Then, the signal corresponding to the button 20Sa is similarly transmitted, applied to the upstream control signal detection circuit 58, and further transmitted to the AND gate 60.

However, since the secret output cuff 00, which is the other input of the AND gate 60, is the signal XXO'' at the timing T1 corresponding to the button 20Sa, it is not output to the AND gate 60, and therefore is not output to the logic gate 641. No input is made and the cross point 561 is never closed.

Therefore, the button telephone 20 realizes a secret function in that it cannot be connected to the central office line 1 as long as another button telephone (19 in this case) is using this central office line.

However, here, the key telephone 20 is, for example, a central office line 2
If it is empty, press button 20Sb corresponding to central office line 21.
As for connecting to the central office line 2 by operating the uplink control signal detection circuit 58, the output of the uplink control signal detection circuit 58 is not inhibited by the AND gate 60 by the confidential signal output cuff 00', and therefore, the output is turning on balanced crosspoint 562 through AND gate 642;
It is possible to connect to the central office line 2.

Next, when the button telephone 19 is turned on-hook, the hook switch 198c becomes a signal 0, and the input to the hook switch signal detection circuit 61 is stopped through the upstream control signal transmission line 29, so the output of this detection circuit 61 is also stopped, and therefore the balance is balanced. The shaped cross point 551 is disconnected because the supply of holding current is cut off.

Then, in the office line circuit 3, current no longer flows through the resistor 101, so the voltage at both ends becomes zero, and the call signal detection circuit 10
2 stops, the line relay 103 is restored, and the output to the common line 500 through the AND gate 104 is also stopped. Therefore, the timing T1 corresponding to the central line 1 with respect to the output of the secret signal detection circuit 600 is stopped. The output becomes signal 1 and deconfidentiality is released.

Therefore, in this state, you can access the central office line 1 from any key telephone.
It becomes possible to connect to.

By performing the above-mentioned movements, it is possible to carry out a secret call operation for the central office line 1, and furthermore, the same operation is possible for other central offices only with different timings.

Further, when adding a confidential function to an extension call, it is only necessary to output the communication to the common line 500 at the timing assigned to that extension only when the extension is desired to be kept confidential.

In this case, when two telephones on an extension line are connected to each other, it is detected that an extension call is being made, for example, based on the value of the current flowing through the connection in the extension circuit, and a confidential signal is output to set the phone to a confidential state. .

Furthermore, if a de-pricing function is added to the office line or extension line, output to the common line 500 may be stopped in each office line circuit or extension circuit when de-pricing the de-pricing.

By carrying out the above-described operations, the confidential conversation function can be easily realized by performing a logical AND operation once for the button signals of each button telephone.

FIG. 4 shows another embodiment of the present invention, and the same parts as in FIG. 2 are given the same reference numerals.

200 is a cross point group, each cross point 551
552.561.562, AND gate 63
3,634, 643, 644 are provided, and one input terminal of these AND gates 633, 634 is connected to the output terminal of the uplink control signal detection circuit 57 to form an AND gate (643, 64).
One input terminal of 4 is connected to an output terminal of an uplink control signal detection circuit 58.

Further, the other input terminals of the AND gates 633 and 643 are connected to the output terminal of the AND gate 801.
4,644.

At one input terminal of the AND gates 801 and 802,
Timing pulses TI and T2 are input, and the other input terminal is connected to the output terminal of the AND gate 81.

One input terminal of this AND gate 81 is connected to the output terminal of the secret signal generation circuit 600, and the other input terminal is connected to the output terminal of the OR gate 82. It is connected to the output terminals of the control signal detection circuits 57 and 5B.

In such a configuration, the cross point group 200 is
In this method, the cross point at the intersection is specified by specifying the row and column when specifying the cross point.

To operate FIG. 4, for example, when the button telephone 19 makes a call to the central office line 1, when the button telephone 19 goes off-hook and presses the button 19S corresponding to the central office line 1, a hook switch signal is detected as described in the explanation of FIG. Circuit 61 applies voltage to balanced cross points 551 and 552 via transformer 49.

In addition, the button signal passes through the upstream control signal detection circuit 57,
A cross point drive signal on the row side is given to the cross point group 200, and it is taken by the AND gate 81 with the secret signal output cuff 00 through the OR gate 82, and further logically with the timing T1 corresponding to the central line 1. The product is obtained by an AND gate 801 and used as a column-side cross-point drive signal.

If we ignore the delay caused by each logic gate, the AND gate 80
The column side cross point drive signal which is the output of the cross point group 2 is generated simultaneously with the row side cross point drive signal which is the output of the uplink control signal detection circuit 57.
Since both inputs of the AND gate 633 in 00 become signal 1 at the same time (more specifically at timing T1),
The output of the AND gate 633 occurs, thereby turning on the balanced crosspoint 551 and thus connecting it to the central office line 1 from the handset 13 of the key telephone 19 through the crosspoint 551, as described below in FIG.

At this time, a row-side cross-point drive signal corresponding to office line 1 is also generated for the cross-points of other key telephones.

For example, the cross point 56 corresponds to the button telephone 20.
One input of AND gate 643 for driving 1 is generated.

However, at this time, if the button telephone 20 is operating a button corresponding to the central office line 2, and the output of the uplink control signal detection circuit 58 generates the other input of the AND gate 643, these two AND gate 643
Since the inputs of will have different timings, the output will not occur,
Therefore, cross point 561 is never closed.

If two key telephones operate the same central office line button at the same time, it is unavoidable that both are rarely connected at the same time.

Now, returning to the beginning of the explanation of FIG.
An output of 1 is not produced, so crosspoint 551 is never closed.

Because of the above-described operation, the secret call function can be realized with one circuit of the AND gate 81 for the entire key telephone device.

As described above, in the present invention, in a button telephone device in which the main device and the key telephone operate at the same timing, the main device receives multiplexed button signals from the key telephone. By creating a secret signal with the same timing at , and by taking the logical product of both, there is no need to take logic for each cross point, and it is extremely easy to do so by simply providing a logic gate for each button telephone. Confidential conversation function can be realized.

Furthermore, as another feature of the present invention, when a matrix-structured crosspoint is adopted in which the crosspoint of the intersection point is specified by specifying the row and column for the crosspoint specification, the line input is performed using the button from the button telephone. By using the signal as it is and logically ORing the button signals of all button telephones, logically ANDing the result with the secret signal, and then inputting the separated signals at each timing as a column input, It is possible to perform secret logic even more intensively, and the secret function can be realized very easily.

As described above, according to the present invention, by creating a secret signal with the same timing as that of the key telephone in the main device, it is not necessary to take logic for each cross point, and the secret call operation can be performed with an extremely simple configuration. It is possible to provide a secret control method for a button telephone device that can significantly simplify the control circuit portion of the button telephone device and reduce the number of failures.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a key telephone device to which the present invention is applied, FIG. 2 is a block diagram showing a secret control method of a key telephone device according to an embodiment of the present invention, and FIG. FIG. 4 is an operational waveform diagram for explaining the operation of the above configuration, and FIG. 4 is a configuration diagram showing another example of the present invention. 1.2... Office line, 3, 4... Office line circuit, 5... Call cross point, 6...
Extension circuit, 7... Extension calling circuit, 8...
- Calling cross point, 9... Office line calling circuit,
10A, IOB, 11A, 11B. 12A, 12B... terminal circuit, 13, 14, 1
5...Transmitter/receiver, 16, 17, 18...
Calling speaker, 19.20,21...button telephone, 19S20S, 21S...button switch, 22...main device, 23,24,25...
...Call audio transmission line, 26, 27, 28...
Calling voice transmission line, 29°30.31...Uplink control signal transmission line, 32,33°34...Display element, 35,36,37...Downward control signal transmission line,
45, 46...Parallel-serial conversion circuit, 551.5
52,561.562...Balanced cross point, 57,58...Uplink control signal detection circuit 59
, 60...... AND gate, 61, 62...
...Hook signal detection circuit, 631.632,641. 642......AND gate, 100...
Transformer, 101... Resistor, 102...
・Call signal detection circuit, 103... Line relay, 104... AND gate, 300...
- Timing pulse generation circuit, 500...Common line, 600...Secret signal generation circuit.

Claims (1)

[Scope of Claims] 1 A button telephone and the main device are connected by three pairs of lines, and a speech voice transmission line and a control signal are exchanged between the button telephone and the main device by multiplex transmission on the three pairs of lines. An uplink control signal transmission path and a downlink control signal transmission path are provided, and the main device is connected to a central office line circuit and an extension circuit for internal phone calls, and the three-pair voice transmission path is connected to the central office line circuit and the internal phone line circuit. In a button telephone device, a call cross point is provided, each timing pulse is assigned to each office line and extension line, and a button signal multiplexed with this timing pulse is sent from the button telephone as an uplink control signal. , supplies assigned timing pulses to each of the office line circuits and extension circuits, and when each office line circuit and extension circuit are in a call state, a logical product of the timing pulse and the call state is applied to each of the office line circuits and extension circuits. means for taking the signal and outputting it to the common line, means for creating a secret signal by inputting the signal from the common line, and an AND gate corresponding to the button telephone, and the AND gate multiplexes the signals from the button telephone. A confidential communication control method for a button telephone device, comprising means for obtaining a control signal for a communication cross point by performing a logical product of a button signal and the confidential communication signal. 2. Use a matrix-structured call crosspoint that specifies the connection of the crosspoints at the intersection by specifying the row and column, and the button signal from the button telephone is used as the row designation signal. Directly used, the column designation signal is the logical sum of the button signals from each button telephone, and then the logical product with the confidential signal.
A confidential communication control method for a button telephone device, characterized in that the outputs are separated into signals according to the timing of the corresponding office line or extension line.