JPS5834075B2 - Call method of button telephone device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a key telephone device that selectively connects a plurality of key telephones to a main device, a plurality of call lines, and a plurality of control lines to a plurality of central office lines or extension lines. It is related to the method.

Hands-free response and communication when an extension call is made using the button telephone device 2 have conventionally been constructed using a circuit system, an example of which is shown in FIG.

In Figure 1, 1 is a counting circuit, 2 is a decoder, 3,4°16 is an amplifier, 5 is a hybrid circuit, 6 is a relay, 6-1 is its connection, 7 is a transformer, 8 is a transistor, 10 is a power supply, 11 , 13 are hook switch contacts, 12 and 14 are phone call circuits, 17 are speakers, 18 are microphones, 19° 20, 21, and 22 are cables, 100 is a main device side control circuit, 200 is a caller side telephone circuit, 300 is the called telephone circuit.

Therefore, in the circuit example shown in FIG. 1, when the transmitter telephone 200 is raised and dialed, the dial pulse operates the relay 6, which connects and disconnects the contact 6-1, and the counting circuit 1 counts the state of the dial pulse. is developed by the decoder 2, and the output signal of its unique output terminal is guided to the base of the transistor 8, which is turned on.

As a result, the transmission signal from the calling telephone 200 is [Telephone circuit 1
2 → Switch 11 → Cable 21 → Hybrid circuit 5 → Amplifier 4 → Transformer 7]
The primary winding is excited, which is induced in the secondary winding, and the induced output is [secondary winding of transformer 7 → cable 19 → earth E → power supply 10 → transistor 8 → secondary winding of transformer 7]. Amplifier 1 is input to the input terminal of amplifier 16 at the root.
6 is amplified and the speaker 17 is sounded.

Also, the transmission signal from the telephone 300 is transmitted from [microphone 18→
The signal is transmitted along the route: cable 20→amplifier 3→hybrid circuit 5→cable 21→hook switch 11→talk circuit 12].

With the above operation, the telephone 200 uses the handset and the telephone 3
In 00, the speaker 7 and the microphone 18 are used to enable communication.

However, this system requires a cable 20 for transmitting microphone signals, and further has drawbacks such as being unable to count other transmissions because the transmitting width counting circuit 1 is captured.

Furthermore, conventional button telephone devices use cables with a large number of core wires to connect the main device and the telephone.

However, in recent years, systems have become larger and more multifunctional, and materials and labor costs have also increased, leading to an increase in system costs.

Therefore, taking measures to reduce the number of cable core wires is an effective means for reducing costs.

Therefore, as a means of reducing the number of cable cores, it is common to move the switching of communication paths such as office lines from within the current telephone set to the main unit, as is generally used in exchanges and the like.

However, this conventional method has the disadvantage that the main device becomes large and expensive.

The present invention provides a communication system in a button telephone device that can greatly reduce the number of cable cores between the main device and the telephone.

The present invention will be explained in detail below with reference to the drawings.

FIG. 2 shows an embodiment of the present invention, in which 1 is a counting circuit, 2 is a decoder, 51 is a relay, and 51-1 is its connection, 30
, 60'', 66 is the hook switch contact, 29.58 is the telephone communication circuit (including dial), 6162 is the amplifier,
63 is a speaker, 64 is a microphone, and 65 is a hybrid circuit 67, 68, 69.

72, 73, 74 are cables, 56 is a flip-flop, 54, 55 are analog switches (thyristors, etc.) compatible with telephones, 52, 53 are telephone switch control circuits compatible with telephones consisting of shift registers, etc., 57.5
9 is a line control circuit, 75 is a transistor, 76 is an inverter, 101 is a main device, 201 is a calling telephone, 30H-
J: Called telephone.

During operation of the embodiment shown in FIG. 2, the line control circuit 57 includes means such as a telephone key, which is activated by operating it, and transmits its output signal to the main device 101 via the cable 68. Since the input is input to the call switch control circuit 52 and the output thereof is configured to open/close the analog switch 54, by raising the handset on the calling telephone 201 and operating the telephone key of the line control circuit, the analog Switch 54 is closed.

Next, when dialing on the calling telephone 201, the dial impulse is [talking circuit 29 → switch contact 3]
0 → cable 67 → relay 51] route to relay 51
is operated, its contact 51-1 is turned on and off, and the counting circuit 1 counts it.

This counting result is developed by the decoder 2, one output terminal of which is input to the set terminal of the flip-flop 56, and its output is input to the gate terminal of the analog gate 55, which is closed.

As a result, the transmission from the calling telephone 201 is [Telephone circuit 2
9 → Switch contact 30 → Cable 67 → Analog switch 54 → Analog switch 55 → Cable 72
→Full switch contact 60→Hybrid circuit 65→
Amplifier 61→Speaker 63] makes the speaker 63 sound.

In addition, transmission from the called telephone 301 is performed using the microphone 64 →
A hands-free call is transmitted via the route of amplifier 62 → hybrid circuit 65 → hook switch contact 60 → cable 72 → analog switch 55 → analog switch 54 → cable 67 → hook switch contact 30 → call circuit 29], and the calling telephone 201 Answer the call using the handset.

The output signal of the input flip-flop 56 is connected to the reset terminal H of the counting circuit, and the output signal of the flip-flop 56 resets the counting circuit 1.

As a result, the counting circuit 1 can then prepare for another dial counting.

Further, even if the counting circuit 1 is reset as described above, the above-mentioned communication state is maintained by the flip-flop 56.

Next, when the called party presses the telephone key included in the line control circuit 59 and raises the handset in order to switch from a hands-free call to a call using the handset, the output signal of the flip-flop 56 changes from [cable 73 to switch contact 66. -> cable 74 -> reset terminal of flip-flop 56] and is applied to the reset terminal of flip-flop 56 to reset it.

At this time, the analog switch 55 inputs the output signal of the line control circuit 59 to the line switch control circuit 53 via the cable 69, and sends the output to the gate of the analog switch 55, as in the case of the calling telephone 201 described above. Lead to close it.

As a result, the communication between the calling telephone 201 and the called telephone 301 via the handset is as follows: ] route, making it possible.

The overall operation of the present invention has been explained above, and in FIG.
69→53→55] will be explained in more detail with reference to FIG.

FIG. 3 shows a call control system using a thyristor as the analog switch.

In Figure 3, 501.527 is a counter, 502.526 is a clock pulse generator, 503.504.528 is a decoder, 510.581.583 is an inverter, 508.
511,514゜515.531 is an and gate, 50
7,509° 512.532 is an OR gate, 513 is a shift register, 519,580 is a transformer, 529 is a telephone communication circuit, 530,536 is a hook switch, 53
3,534 is the contact point of the telephone key for selecting the central office line (or extension line), 53
5 is a power supply, 540 is a flip-flop circuit, ■ is the (G) side of the power supply, E is the (→ side of the power supply, 584 is a transistor, 554-1.554-2 is a thyristor, 585, 58
6°587 is a resistor.

To operate the above circuit, first, set the counter 5.
01 and 527 are clock pulse generators 50, respectively.
2 and 526 output pulses are counted, and further assume that they are synchronous.

Now, in order to talk to the central office line, when the handset is raised and the telephone key for selecting the central office line is pressed, contacts 533 and 534 become connected.

As a result, the timing pulse T91 of the output signal from the decoder 528 driven by 1 by the output signal of the counter 527 is [decoder 528 → contact 533 → OR gate 5
32 → AND gate 531 → flip-flop 540
] is applied to the input terminal of the flip-flop 540.

As a result of the above, a signal for selecting a central office line (or extension line) has been sent from the telephone to the main device.

The sent signal is received by the main device and transferred to the shift register 51.
3 is stored.

Now, the timing for inputting to the shift register 513 will be explained.

First, the counter 501 has a plurality of cascade-connected binary numbers.
A clock pulse generator 50 consisting of a counter
It is driven by the clock pulse train CP which is the output of No. 2.

A time chart of the outputs C1 to CIO of the counter 501 is shown in FIG.

Next, the output of the counter 501 drives the decoder 503 and the decoder 504, and the respective outputs t1 to tn, T
1 to obtain Tn.

Here, T1 to Tn are signals whose pulse width is the period of the output CIO of the counter 501, as shown in FIG. 4(2).

Further, as shown in FIG. 4 (5), t1 to tn are signals whose pulse width is equal to the period of CP, and the pulse widths of t1 to tn are sufficiently small compared to the pulse widths of T1 to Tn.

Furthermore, signals T1' to Tn/ from the telephone and T1 to Tn
The relationships shown in FIG. 4 (2) and (3) exist between them, and they are synchronized with a certain delay.

FIG. 4(1) is a diagram showing the data timing in the case of five office lines, and in the figure, LK1 to LK indicate signals for the office line telephone keys, respectively.

Further, T indicates a unit time of time slots T1 to Tn.

As is clear from this figure, the transmission signal T9' from the telephone to the main device is delayed by a certain period of time with respect to T.

This delay can be avoided by receiving signals near the center of the pulse width when the main device receives the pulses.
This is to correct the synchronization error of 7.

In FIG. 3, the flip-flop 540 is connected to the gate pulse CI
It is of the type that is output when O rises.

Therefore, as mentioned above, when the input signals T and l are applied here, they are output to the output side of the flip-flop 540 in synchronization with the gate pulse C1o, and are applied to one of the input terminals of the analog gate 511. be done.

The output signal at this time is synchronized with the CIO.

Here, C1o is the output of the counter 501.

Next, the output of the shift register 513 forms a feedback loop in the loop of [output terminal of shift register 513 → AND gate 514 → OR gate 512 → input terminal of shift register 513], and the shift register 513 shifts with the clock pulse CP. The information input to , here is configured so that it is circulated and stored at a constant cycle.

Therefore, in order to input the signal to the shift register 513, a timing pulse is output from the OR gate 509 by a circuit constituted by an AND gate 508 and OR gates 507 and 509, and one of the output signals is sent to the inverter 5.
10 to AND gate 514 to close it.

The other side is applied to the AND gate 511, which is opened so that the signal applied from the flip-flop 540 is passed through the OR gate 512 to the shift register 5.
13.

5, this input timing is determined by tl and t as described above.
2, the storage position in the shift register 513 is also fixed, and is output at a timing of 11.12 after - period.

In order to synchronize the input and output of the shift register 513, the storage capacity of the shift register 513 is increased by the decoder 50.
The setting is the same as steps t1 to tn of one cycle of No. 3.

As described above, the office line signal T9I input from the telephone is converted into timings tl and t2, which are further converted to tl by the AND gate 515 with a pulse at timing C1.
The output is applied through resistors 585 and 586 to the respective gate terminals of thyristors 554-1 and 554-2, turning them on.

Therefore, between the anode and cathode respectively [power supply → resistor 587 → right winding of transformer 580 → thyristor 5
54-1 (or 554-2) → left winding 519-1 of transformer 519 → collector-emitter of transistor 584 → earth E], a direct current flows, turning on thyristors 554-1 and 554-2. The state is maintained, and the AC signal induced in transformer 580 is transmitted to transformer 519.

Next, when the telephone key is pressed, for example, when the telephone key 533 changes from closed to closed, the state of the shift register 513 changes.

That is, although the signal from the telephone is cut off, the shift register 513 stores a signal corresponding to the state of the telephone key 533 for one period, so the output of the AND gate 511 in FIG. The output of 513 is the corresponding time slot (in case of
, the former becomes low level and the latter becomes high level.

The state is detected by an AND gate 582, and its output is applied to the base of a transistor 584 through an inverter 583.

Here, when there is no input to the output terminal of the inverter 583, a high level, that is, a positive voltage is applied, and when a pulse is input to the inverter 583 in the above operation, its output becomes a low level, that is, the ground potential.

As a result, the collector-emitter of the transistor 584 is turned off when the pulse is present, which cuts off the DC loop current flowing through the thyristor 554-1.554-2 and turns off the thyristor 554-1.554-2. do.

Through the above operations, it becomes possible to control the communication path switch (Sirisk switch) installed in the main device using the communication path control electric key, that is, the office line (or extension line) electric key installed in the telephone.

The above operation was explained for the operation when changing the telephone key, but even if suddenly generated external noise etc. enters the control circuit and the wrong communication path switch is closed, such a signal will be ignored. Since this is not continuous, the operation is similar to that described above, and the transistor 584 is momentarily cut off, turning off the thyristor.

In other words, it operates as an error detection function, and even if an erroneous channel switch is closed, it will be opened after one cycle.Furthermore, by setting the cycle of the write control signal sufficiently short, this instantaneous erroneous connection can be avoided in practice. It's not a problem.

In addition, in FIG. 3, a case has been explained in which a thyristor is used for the analog switches 54 and 55 in FIG. A similar effect can be obtained by inserting the antenna into the base of the communication channel control circuit 52, 53 and the output terminals of the communication path control circuits 52 and 53.

In addition, in FIGS. 2 and 3, when the telephone 301 responds with a handset, the reset signal for the flip-flop 56 is branched from the cable 74 and is ORed to the input of the inverter 583 in FIG. By inputting this, the collector-emitter of the transistor 584 is momentarily disconnected, and the thyristor can be turned off in the same manner as the operation when changing the electric key described above.

Further, in FIG. 2, a flip-flop is set to the reset terminal R of the flip-flop 56, and a timer circuit that outputs an output signal after a certain period of time is connected in parallel, so that the hands-free calling is started after a certain period of time has elapsed after the start of the hands-free calling. Can be stopped.

Next, regarding the power supplies of the amplifiers 61 and 62, the above explanation assumes that the power/reflection has already been applied.Controlling the power/reflection to be applied when the calling signal is input will reduce the power consumption, noise, etc. is also valid.

As an example of this control, an amplifier 6 is used as shown in FIG.
A transistor switch 75 is arranged at the power input terminals 1 and 62, and the output signal of the flip-flop 56 is transmitted to its base via the route [flip-flop 56 → cable 73 → inverter 76 → base of transistor 75]. When the output is at a high level, the base potential of the transistor 75 is grounded, the collector and emitter of the transistor are turned on, and the amplifier 61 and 62 are →Earth] power is applied through the route.

Further, when the output of the flip-flop 56 is at a low level, the collector-emitter of the transistor 75 is disconnected through the route, and the power to the amplifiers 61 and 62 is cut off.

With the above operation, it is possible to control the power of the amplifiers 61 and 62 to be turned on at the time of the call.

In FIG. 2, cables 73 and 74 are connected to cable 6 by using the method used in FIG. 3, that is, by using the time division transmission method.
9 can be shared and can be omitted.

Figure 3 shows the case where there is one line (or extension line) and one telephone line, but when there are multiple lines (or extension lines) and telephone lines, the SIRISK switch is It is sufficient to construct a matrix circuit in which the number of office lines (or extension lines) is multiplied by the number of telephones.

Figure 3 shows an example of a case where a thyristor is used as a communication path switch. Figure 5 shows an example of a configuration in which a thyristor is used in place of the thyristor, and an analog switch such as a transistor switch is combined with a memory element such as a D-type flip-flop. In this case, the above-mentioned flip-flop is set only when there is an output signal from the gate 515 in FIG. 3, and its output closes the analog switch to form a communication path.

Therefore, in FIG. 5, the output signal of gate 582 of FIG. 3 is unnecessary.

In Figure 5, 601 is a D-type flip-flop, 602.6
03 is a transistor.

Now, an output is obtained from the shift register 513 in the same manner as in FIG. 3, and is applied to the signal input terminal of the D-type flip-flop 603.

On the other hand, by applying a signal of 1 to the time slot to its clock terminal, the D-type flip-flop 601 is set, and its output signal is transmitted to the transistors 602 and 60.
3, turning it on.

Through the above operations, a communication path is formed in the same manner as in FIG. 3.

Figure 6 shows a transistor and R instead of the thyristor in Figure 3.
This is an example of a circuit constructed by combining S flip-flop circuits. Its operation is to input the output signal of the second gate 515 to the set terminal of the RS flip-flop 604, set it, and reset it. gate 58
2 to the reset terminal of RS flip-flop 604 to reset it, and by applying the output signal of RS flip-flop 604 to the gates of transistors 602 and 603. is turned on, and a communication path is formed in the same manner as in FIG.

FIG. 7 shows a modification of FIG. 3, in which, instead of directly inputting central office line key information from a telephone into the circulating memory, it is first inputted to a processing device, etc., and after the necessary processing is performed, the CPU
This method is a method in which the output is manually entered into a circulating memory, and this method is a practically effective means when combining the functions of the present invention with other functions such as a secret call function in a key telephone device.

The differences between FIG. 3 and FIG. 7 are summarized below.

Figure 3 shows that by providing a circulating memory corresponding to a telephone set, a memory area corresponding to the telephone set is determined, and a memory area in the circulating memory for storing central office line key information is divided into a time slot and a central office line key that determine the memory area of the circulating memory. This method detects the arrival of the central office line telephone key information by performing a logical product with the time slot that conveys the information, and stores it in a designated memory area of a circulating memory.

On the other hand, in Fig. 7, the telephone key information coming from the telephone is once input to the processing device, and after the necessary processing is performed, the output signal is used to latch the memory that latches the information corresponding to the telephone and the office line information. In this method, the memory area of the circular memory is determined by logical product of the two pieces of information plus a time slot that determines the memory area of the circular memory, and the memory is stored there.

Here, while FIG. 3 is constructed of wired logic, the processing device of FIG. 7 is generally stored program logic.

Next, the circular memory shown in Fig. 7 is an example in which one shift register is used for each telephone set.In this case, the output of the processing unit is encoded, and information corresponding to the telephone set is input into the shift register in the form of a code. By decoding the output and expanding it into information corresponding to each telephone, it is possible to reduce the memory capacity.

The configuration and operation of the embodiment shown in FIG. 7 will be described in detail below.

In FIG. 7, 701 is a processing device, 702, 703, 704
, 705, 706 are latch memories composed of D-type flip-flops, etc., 707, 708° 709. 713, 7
14 is an AND gate, 710 is an inverter, 711,7
18 is an OR gate, 712 is a shift register, 715 is a photocoupler, and 717 is the same flip-flop as 540.

The difference between FIG. 3 and FIG. 7 is that in FIG. 7, a shift register 5 is connected between the flip-flop 540 and the AND gate 511 in FIG.
13 control circuits 702, 703゜705, 707,
This is the point where 708 and 718 were inserted.

Therefore, in FIG. 7, office line key information from the telephone is output to flip-flop 540 in the same manner as in FIG.

The output signal is inputted to a processing device 701, where it is divided into telephone corresponding information and office line telephone key information under the control of a storage program through flip-flops 705 and 7, respectively.
03 and obtain an output signal at its output terminal.

That is, since the output terminals of flip-flops 703 and 705 each become high level, the data is stored in a predetermined memory area of the shift register 513 in the same manner as in FIG. 3, and the following operation is similar to that in FIG. be.

Another difference between FIG. 3 and FIG. 7 is that in FIG. 3 the contents of the shift register 513 are used as means for controlling the transistor 584, but in FIG. It has a memory of
The output signal of the processing device is applied to the flip-flop 706, which is set, and its output is applied to the base of the transistor 584 via the inverter 583, and the collector-emitter thereof is momentarily turned off.

The following description is omitted since it is the same as in the case of FIG.

Moreover, it is natural that this part can be made as shown in FIG.

As explained in detail above, the present invention can be executed not only by the wired logic method but also by the stored program logic method, and when used in a large-scale system or a system with multiple functions, it is possible to implement the present invention using the wired logic method. This method has advantages over other methods.

In order to turn on the thyristor, the present invention employs a method of repeatedly applying high-speed pulses to the gate of the thyristor. A power tag configured to hold the state. When this is used as a call path switch, if a reverse current higher than the normal call level flows between the thyristor's anode and cathode due to external noise, etc., the thyristor will turn off. .

Therefore, in the present invention, in order to turn on the thyristor again to such an extent that it does not cause a practical problem when such a phenomenon occurs, an improvement is made by applying high-speed repetitive pulses to the gate of the thyristor.

Next, FIG. 7 can be applied to FIG. 2.

When the telephone 301 is called by the telephone 201, when the telephone 201 dials, the dial is counted by the counting circuit 1, the called destination is specified based on the result, and the communication path switch corresponding to the called telephone is turned on.

Therefore, the counting circuit 1 and flip-flop 5 in FIG.
This is possible by using the processing device 701 and shift register 712 shown in FIG. 7 instead of 6.

That is, in FIG. 7, when dialing is performed in the telephone call circuit 529, the dial impulse is inputted to the processing device 701 via the photocoupler 715, processed there, and as a result is stored in the memory area designated by the shift register 712 in the same manner as described above. The output signal is stored in the AND gate 71.
4 to the gate of the call path switch of the called telephone, such as the call path switch 55 in FIG. 2, to turn it on.

Thereafter, hands-free communication is enabled by the same operation as in FIG. 2 described above.

This method is practically advantageous in large systems compared to the case of FIG.

Although the present invention has been described using a shift register as an embodiment thereof, similar effects can be obtained by using other memory means such as random access memory (RAM) and program control by a processor or the like. can.

As described above, the present invention connects a plurality of key telephones to a main device, a plurality of call lines, and a plurality of control lines to connect a plurality of office lines (
In the button telephone device, the main device includes a clock pulse, a plurality of rows of high-speed time slot pulses corresponding to the central office line (or extension), and a plurality of rows of controls corresponding to the control line. a first pulse generator 1゜2.3.4 for generating low-speed time slot pulses for signal transmission; a plurality of memories 13 such as circulating memories provided corresponding to the plurality of button telephones; a plurality of writes for writing control outputs transmitted from the corresponding button telephones via the control lines into corresponding ones of the plurality of memories in synchronization with the plurality of rows of low-speed time slot pulses for transmitting control signals; means? , 8, 9, 10.
IL 40, pulse train signals corresponding to the plurality of trains of high-speed time slot pulses provided corresponding to the office line (or extension) and the telephone, and corresponding to each of the office lines (or extensions), and the output signal of the memory. Switch element 54-1.54 having a holding function controlled by AND output with
-2 and switch means 84 for opening and closing the direct current of the thyristor, and each of the telephones has a synchronization time slot substantially synchronized with a corresponding one of the plurality of rows of low-speed time slots for control signal transmission. second pulse generators 26, 27, 28 for generating pulses; operating means 33, 34 including a plurality of office line (or extension) selection telephone keys corresponding to the office line (or extension); control output means 31, 32, 36 for taking out the control output from the corresponding button telephone by AND output of the output and the synchronized time slot pulse; This is a telephone communication method for a key telephone device, which is configured such that one of the office lines (or extension lines) specified by the control output sent out is connected to the key telephone and a telephone conversation can be made.

Further, the switch means may be attached with a control means 81.82 which outputs an output when the content written in the memory changes and controls the opening/closing of the switch element 54-1.54-2 based on this output. can.

As explained above, the present invention can significantly reduce the number of cable cores between the main device of a button telephone device and the telephone, which conventionally used a large number of cable cores, resulting in resource saving, cost reduction, The practical effects such as improved reliability are significant.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional example related to the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIGS. 3 and 7 are circuits showing specific examples of communication path control in FIG. 2. figure,
FIG. 4 is a time chart explaining the operation of the example shown in FIG. 3, and FIGS. 5 and 6 are circuit diagrams showing a partial modification of the specific example shown in FIG.

Claims (1)

[Scope of Claims] 1. In a button telephone device in which a plurality of key telephones are selectively connected to a main device and a plurality of office lines or extension lines using a plurality of call lines and a plurality of control lines, the main device a first pulse generator for generating clock pulses, a plurality of rows of high-speed time slot pulses corresponding to the office line or extension line, and a plurality of rows of low-speed time slot pulses for control signal transmission corresponding to the plurality of control lines; and a plurality of memory such as a plurality of circulating memories provided corresponding to the plurality of button telephones, and a control output transmitted from a corresponding one of the plurality of button telephones via the control line. a plurality of writing means for writing into a corresponding one of the plurality of memories in synchronization with a low-speed time slot pulse for control signal transmission; and a plurality of writing means provided corresponding to the office line or extension line and the telephone set; a switch element having a holding function controlled by an AND output of a corresponding pulse train of the plurality of high-speed time slot pulses corresponding to each of the extensions and an output signal of the memory; and a switch means for controlling opening and closing of the switch element. and each of the plurality of button telephones has a second one for generating a synchronous time slot pulse that is synchronized with a corresponding one of the plurality of rows of low-speed time slot pulses for transmitting control signals.
a pulse generator, an operating means including a plurality of selection telephone keys corresponding to a central office line or an extension, and an AND output between the output of the operating means and the synchronization time slot pulse to select one of the plurality of button telephones from the corresponding one of the telephones. and a control output means for taking out a control output, so that one of the office lines or extensions designated by the control output sent out by a selection operation using the selection telephone key is selected from among the plurality of key telephones. 1. A telephone call system for a button telephone device, characterized in that the key telephone device is configured to be connected to the operated button telephone and make a telephone call. 2. The button according to claim 1, wherein the switch means includes a control means that takes out an output when the content written in the memory changes and controls opening and closing of the switch element based on the output. Telephone device communication method.