JPS5950152B2 - Confidential communication method in button telephone equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a button telephone device, and more particularly to a button telephone device suitable for small businesses or residences.

Conventional button telephone devices of this kind are configured to be wired using multi-core cables with about 20 core wires, so wiring work is not easy, and the arrangement of multi-core cables can spoil the aesthetics of the room. Moreover, it also had the disadvantage of increasing construction costs.

In order to eliminate these drawbacks, there is a desire to reduce the number of core wires in distribution cables, but conventionally information between the main device and each slave device was transmitted in parallel within a multi-core cable. Therefore, when reducing the number of core wires, it is necessary to multiplex and transmit this parallel information. However, if all the information is multiplexed and transmitted over the information line, the configuration of the circuit used for information transmission becomes complicated and the cost increases. SUMMARY OF THE INVENTION An object of the present invention is to provide a confidential communication system in a button telephone device that can reduce the number of core wires of a wiring cable with a relatively simple circuit configuration.

The present invention will be explained in detail below.

First, the principle of the entire system of the key telephone device according to the present invention will be explained.

In the present invention, information from the main device to the slave device and information from the slave device to the main device are divided into two blocks, and lamp and amplifier operation information from the main device to the slave device is multiplexed and sent to the information line. We decided to send button selection, hold, and dialing information from the handset to the main unit using the telephone line. The communication current of the telephone line is varied by a constant current circuit in the handset, and button selection, hold, and dial information are identified by a detection circuit in the main unit. Putting the above together, 2 central lines and 1 extension line
The table below shows the case of a button telephone device that accommodates lines and connects three handsets. Table 1 clarifies the information and transmission routes, and Table 2 shows an example of the relationship between the status of each handset and the communication current with respect to information sent over the communication line. The basic matters used in the present invention, including the type of transmission line, are listed below.

(1) The communication path is selected by switching one line at a cross point using SCR. (2) The selection of office line 1, office line 2, and extension line is made by identifying the difference in communication current.

(3) The determination of the communication current in order to accurately detect the difference in communication current as described in item (2) is performed by a constant current circuit using an operational amplifier in the handset.

(4) When using the cross-point switching method using SCR, transmission of dial pulses from slave units is an extremely difficult problem.

In the case of a normal telephone, when the communication current is cut off during dialing, the holding current of the SCR is cut off, and the formed cross point is canceled. In order to solve this problem, by controlling the constant current circuit on the handset side, a talking current equivalent to the self-holding current of the SCR cross point will flow even when the current is interrupted by the dial, and a predetermined talking current will flow when the dial is connected.
The difference is identified within the main device and the pulse is relayed to the line.
(5) For hold, when you press the hold button, the constant current circuit inside the handset is controlled, and the call current is set at 20m compared to the normal call current.
Increase by about A and detect this.

1(6) When there is a handset detection output on both the office line and the extension line and the trunk is empty, a trigger is input to the cross point SCR to capture the line, otherwise the line is not captured and the communication is kept confidential.

7 (7) Individual extension calls and simultaneous calls to slave units are made by dialing a single digit.

(8) In the main device, voice calling of extension lines, transmission of incoming tone, etc., and selection of handset are performed by cross-point control.

(9) Information transmission via the information line is unidirectional from the main device to the slave device, and is performed by time division multiplexing.

The information content is 3 bits for lamp information of office line 1, office line 2, and extension line, and 1 bit for amplifier operation information, making a total of 4 bits and 1 frame. 1 Based on the above principles, we will explain in more detail regarding the transmission of information between the main unit and each slave unit.

First, since the dial pulse transmission method uses the call-to-call method, it is necessary to relay the dial pulses sent from the slave units to the line within the main unit.

In addition, since SCR crosspoint control is used to connect the handset and the central office line trunk, if the dial pulses caused by connecting and disconnecting the call current are sent directly from the handset to the main unit as in conventional telephones, the call current will be reduced. When the SCR is disconnected, the holding current of the SCR is lost, so the SCR is restored and the call loop is broken. To solve this problem, a current of about 7 mA, which is higher than the holding current (5 mA) of the SCR, flows even when the call current is cut off during dialing, and when the call current is connected (40 or 30 mA).
) is streamed as is, the difference is detected and relayed to the line. FIG. 1 shows the change in communication current and the detection level of the office line detection circuit when dialing the office line 1 from the handset.

Regarding station line hold, the constant current circuit of the handset is controlled so that when the hold button of the handset is pressed, the call current increases by 20 mA from the normal call current, and this increase is detected within the main device.

On the information line, a total of 4 bits of information, 3 bits of lamp information and 1 bit of amplifier operation information, sent from the main device to the slave device are time-division multiplexed and sent.

Regarding the synchronization method, it is impossible to send the synchronization signal over a separate line, and since the start-stop synchronization method would complicate the circuitry of the handset, it is decided to send the information signal and the synchronization signal at the same time.

The synchronization signal is sent as a pulse with a level of about 10V, and the information signal is sent as a pulse with a level of about 24V superimposed on the synchronization signal, which is separated into a sinus pulse and an information pulse in the slave unit and used. Regarding the reset pulse, approximately 8 bits per frame are used for the information amount of 4 bits on the information line, and 4 bits are used for each frame.
As for the bit, there is also no synchronization pulse, and a reset pulse is generated within the handset when synchronization pulses are not present continuously. FIG. 2 shows an overview of the information content of the information line and the information processing within the handset.

In accordance with the above principle, the button telephone device according to the present invention can be constructed as shown in FIG.

The main unit and each slave unit #], #2, and #3 are each connected by four wires. The four lines are the power (G) line P, the communication line T, the information line J, and the power (G) line G from the top of the figure. Ru.

Power is sent through the power (G) line P and power (C) line G, and communication current is sent through the power (G) line P and the communication line T. Also, depending on the difference in the current flowing through the communication line T, information is sent from the slave device to the main device. Information sent from the main unit to the slave unit is sent as a 4-bit multiplexed signal through the information line. Ru. An incoming tone signal indicating an incoming call from the central office line and a voice signal when an extension is called are sent through the telephone line T and the power line G, and are sent to the handset amplifier 2.
4 and sent out from the speaker 25. The lamp status signal from the main device to the slave unit and the signal for operating the slave unit amplifier are as follows: [Slave unit lamp control circuit 9 → Incoming tone circuit 1
0→parallel/serial conversion circuit 14→information line J→serial/parallel conversion circuit 23], each lamp 31 in each child unit,
32, 33 and slave amplifier 24. The button selection information, central line capture and abandonment information, dial information, and hold information sent from the handset to the main device are controlled by the call current control circuit 21 in the handset and button or dial operations to control the call current to a set current value. Each slave device detection circuit 8-1, 8-2, 8-3 in the main device, detection circuit 2-]-2 of station line 1, detection circuit 2-2-2 of station line 2, and It is identified by the extension detection circuit 3-2 and the main device is controlled. Since the button selection information is information before the cross point is formed by the SCR, the handset detection circuits 8-1, 8-2, 8-3
The output forms an SCR cross point, and the trunks 2-1, 2 of central office line 1, central office line 2, and extension line 2-1 and 2-2 are identified by
-2 and 3 are connected to the respective station lines. When a cross point is formed by SCR and a communication path is established, handset detection circuits 8-1, 8-2, and 8-3 are separated from the communication path, and instead detect each of the office line 1, office line 2, and extension line. Circuit 2-]
-2, 2-2-2, and 3-2 are in operation to identify and control dialing information, hold information, and abandonment information of central office line extensions. FIG. 4 shows a specific example of the main device in the embodiment of FIG. 3, and FIG. 5 shows a specific example of the slave device.

Next, the operation of the basic functions will be explained.

(Operation of station line transmission) When the station line 1 button of handset #1 is pressed and the handset of the handset is up, the lift switch HS is activated, and the operational amplifier 0P is activated.
A communication current of 40 mA is determined by the resistor R203 of the constant current circuit constituted by the transistor Tr201 and the transistor Tr201, and R204 selected by the button switch LK1, and this is determined by [telephone circuit network TEL → switch LK] → switch switch HS → BS contact. →Talking line T (#1)] flows to talking line T.

In the main device, the output of IC4 is 10W, and since no current flows through the photocoupler PD1, the transistor Trl connected to it is OFF, and the OR circuit 1C2 and N
Through the OT circuit 1C3, the transistors Tr2 and Tr3
is in the ON state. Here, when a communication current of 40 mA flows from the handset, the communication current flows to the resistor R3 through the transistor Tr3, and a voltage corresponding to 40 mA is generated across the resistor R3. Comparator Comp1 in slave device detection circuit 8-1 operates, and its output is input to AND circuit 1C9. In addition, in the detection circuit 2-1-2 of the office line 1, the communication current flows through the transistor Tr3 and the resistor R3, and the transformer LTCO
1 and resistor R8, so the comparator Co
The mp4 is turned off and its output is 10W. The output of the comparator Comp4 passes through a NOT circuit 1C54 and is applied to an AND circuit 1C9. That is, when the trunk 2-1 of the central office line 1 is not in use, the handset detection circuit 8-
When an output to capture station line 1COL1 is added from 1, AN
The D circuit 1C9 is set to a high output and triggers the gate of the SCR of S1 that connects the handset #1 and the central office line 1 trunk 2-1. At the same time, the High output of the AND circuit 1C9 is [OR circuit 1C4 → OR circuit 1C2 → NOT circuit 1C
3] through the path, transistors Tr2 and Tr3 are turned off.
F, and the communication current is [Resistor R4 → Photocoupler PD1 →
S1 SCR → Office line 1 transformer LTCO1 → Resistor, R8
]. When a communication current flows through the photocoupler PD1, the transistor Tr1 is turned ON, and the transistors Tr2 and Tr3 are kept OFF through a path of [NOT circuit 1C1→OR circuit 1C2→NOT circuit IC3]. When a communication current flows through the resistor R8, a voltage is generated across the resistor R8, and the comparator Comp4 operates.
Transistor Tr5 is turned on by the High output,
Relay A1 works. The central line 1C is connected by the contact a1-1.
The line of OL1 is closed, and handset #1 completes acquisition of the office line 1 through the office line 1 transformer LTCO1. Also, A
When relay 1 operates, the lamp signal of station line 1 applied to terminal 4 of data selector IC 67 becomes Hi through contact a1-2.
fgh, the information line J(7) LD1 information becomes High after parallel/serial conversion by the parallel/serial conversion circuit 14. This signal is sent to the slave unit through the information line J, and is separated into a synchronization pulse and an information pulse by comparators Comp201 and Comp202, and the serial/parallel conversion circuit 23
The transistor Tr202 is converted into series/parallel by
Turn the switch to N and turn on the lamp LD1. Here, when handset #1 makes a dial call, contact DP1 opens and closes due to the dial, and when contact DP1 is open, ladder R204 of the handset constant current circuit
is separated by contact DP1, and the communication current is passed through resistor R20.
It becomes 10mA determined by 3.

When the contact DP1 is closed, the current is 40 mA, similar to when talking. Also, contact DP2 connects telephone circuit T during dialing.
Short-circuiting EL not only prevents noise from the receiver due to intermittent current, but also prevents disturbance of the waveform of intermittent current caused by telephone circuit TEL(7)L,C. The intermittent current generated by the dial is sent to the main device through the telephone line T, and this is transmitted to the main device through the telephone line T#1 → resistor R4 → photocoupler PD1 → SCR of S1 →
A voltage pulse is generated across the resistor R8. This voltage pulse is detected by comparator Comp5, and when the communication current is 15 mA or less, comparator Comp5 becomes Hi.
Outputs gh output. The output of comparator Comp5 is N
The transistor Tr6 is turned on through the OT circuit 1C12 and the AND circuit 1C13, and the D1 relay is turned on. The D1 relay contact d1-1 sends out a dial pulse to the line. Since a minimum call current of 7 mA is ensured even during dialing, the current flowing through the SCR of S1 is equal to the SCR.
The minimum holding current becomes 5 mA or more, and the SCR maintains the ON state. When the dialing is completed, the call to the other party is made through the transformer LTCO1. When handset #1 is talking through central line 1, handset #2 attempts to interrupt central line 1 by pressing the button on central line 1 and raising the handset. It operates, and a predetermined call current is passed from the handset side to the call line T#.
2 to the main device.

At this time, in the main device, since the transistors Tr9 and Tr10 of the child device detection circuit 8-2 are in the ON state, a communication current flows through the transistor Tr0 to the resistor R15, and a voltage is generated across the transistor Tr0, and this voltage generates a voltage across the resistor R15. Comparator C
omp7 operates, and the output of comparator Comp7 is A.
The signal is input to the ND circuit 1C10. However, at that time station 1
Transformer LTCO1 is in use by slave unit #1, so it is connected to station line 1.
The communication current from handset #1 flows into the resistor R8 in the detection circuit 2-1-2, and a voltage is generated across the resistor R8.
Therefore, the comparator Comp4 operates, and its output is input to the AND circuit 1C10 through the NOT circuit 1C54. Since this input is at the 10W level when transformer LTCO1 is in use, #2 slave device detection circuit 8-2
AND circuit 1C10 does not open even if there is an output from
No trigger pulse is applied to CR, and slave unit #2 and office line 1 transformer LTCO1 are not coupled. By the above-described operation, the confidentiality of the telephone call on the central office line 1 of the handset #1 is protected. Here, slave #
When 1 puts down the handset, the switch HS (7) turns OFF.
Due to this, the communication current disappears, and the holding current of the SCR of S1 that connects the station 1 trunk and handset #1 disappears.
will be restored.

When S1 is restored, the voltage across resistor R8 disappears, comparator Comp4 turns OFF, and transistor T
r5 turns OFF. Relay A1 is restored by turning off transistor Tr5, and its contact a1-1 is opened to open the line. When the relay A1 is restored, the 1 lamp information is turned OFF by the contact a1-2, and this information is converted from parallel to serial by the parallel to serial conversion circuit 14, and then sent to each slave unit through the information line, The station line 1 lamp on the aircraft goes out. The operation of handset #1 to capture central line 1 from the state in which the handset is initially placed is as described above.
When using a button telephone, for example, when you want to capture the central line 1 immediately after the end of a telephone call on the central office line 2 or extension, you can directly switch from the central office line 2 or internal telephone button to the central telephone line 1 button without putting down the handset. , the acquisition line may be changed. The operation of this device at this time is as follows. Assume that the button for the office line 2 is now switched to the button for the office line 1. While capturing the office line 2, [Power supply line P → constant current circuit → telephone circuit TEL → switch LK2 → switch LK1 → switch HS → BS contact → talking line T#1 → resistor R4 → photocoupler PD1 → SCR of S4 → Office line 2 transformer LTC0
2→resistor R20→earth], when the communication current flows and the office line 2 is captured by the transformer LTCO2,
When the switch LK1 of the station line 1 button is turned on, the station line 1
When the button is pressed, the BS contact in the communication path opens momentarily, cutting off the communication current. Therefore, the cross-point thyristor S4 is restored. Also, since the communication current is cut off, the photocoupler PD1 is turned off and the transistor Tr
1 becomes 0FF. When the transistor Tr1 is turned off, the transistor Tr2 is turned on through the path [NOT circuit 1C1→OR circuit IC2→NOT circuit 1C3].
Transistor Tr3 is turned on. Since the BS contact momentarily turns OFF and then immediately becomes 0N, the communication current determined by the contact LK of the station line] button and the resistor R204 becomes [power supply (G) 1 wire P → constant current circuit → telephone circuit TEL → The signal flows through the following path: switch LK1 -> box switch HS -) BS contact -> communication line T#1 -> transistor Tr3 -> resistor R3 -> ground], and thereafter operates in the same way as the acquisition operation of the central office line 1 described above. (Operation of incoming call on central office line) When an incoming call is received on central office line 1 and a ringing signal is added, relay R1 operates through capacitors C14 and C15, and the output of 0R circuit 1C66 becomes High due to the line point r1-2, and the data selector The slave amplifier operation information applied to the terminal 7 of the IC 67 is turned on.

This information is parallel-to-serial converted by a parallel-to-serial conversion circuit 14 and sent to each child unit through an information line J. On the handset side, the information is serial-parallel converted by the serial-parallel conversion circuit 23, and the transistor Tr205 is turned on to operate the C relay. The amplifier circuit output is connected to the speaker 25 through the contact C, and the amplifier circuit becomes operational. Also, the incoming tone circuit 10 is operated by the rA-2 contact, and the tone ringer signal is amplified by the AMP circuit 11 and sent to the tone sending transformer T. It is input to T. One end of the secondary side of the transformer is given a potential of approximately 5V by a Zener diode ZD4, and the other terminal is connected to the communication lines T#1, T#2, T#3 of all slave units through diodes D6, D7, and D8. It's connected. now,
When handset #1 is not in use, [+5V→Transformer T. Current flows through the path of T→Diode D6→Talking line T#1→Hook switch HS→Resistance R208], diode D6 is turned on, and the tone ringer signal is superimposed on this path and transmitted to slave unit #1. The signal is amplified by the amplifier 24 and the speaker 25 sounds. In addition, when handset #2 is in the middle of a telephone call on the central office line, the communication current is
→ photocoupler ZD2 → SCR of S5 → transformer LTCO2 of office line 2 → resistor R20], so diode D7 is reverse biased and turned off, and tone ringer signal is sent to call T#2 of handset #2. is not sent. Due to the above operation, the call in use will not be affected.
Only the speaker 25 of the handset that is not in use is made to sound.
In addition, for a handset that is preset to stop the incoming station signal, diodes D6 and D7 connect the communication line of the handset.
Alternatively, it is also possible to stop the station ringing tone by not implementing D8. When relay R1 operates, its contact r1
-1, the oscillation circuit 0SC in the slave lamp control circuit 9 (
2HZ), a 2HZ square wave signal oscillates, and the AND circuit I
An intermittent signal of 2Hz is added to the office line 1 lamp information by OR circuit 1C64 with C60. This converts parallel/serial,
The signal is sent to each handset through the information line J, converted into serial/parallel, and the station line 1 lamps of all handsets flash at 2Hz. Here, when handset #1 presses the central line 1 button and raises the handset,
The SCR of S1 performs the operation of transmitting a station line and connects the station line 1 transformer LTCO1 and the slave unit #1 based on the output of the slave unit detection circuit 8-1 and the status output of the station line detection circuit 2-12 of the station line 1.
Apply a trigger to the gate and turn S1 ON.

The communication current flows through the path of [handset #1→talk line T#1→resistance R4→photocoupler PD1→SCR of S1→transformer LTCO1→resistance R8], and the voltage generated across resistor R8 operates comparator Comp4. At the output, the transistor Tr5 is turned on and the relay A1 operates. Rire A
1 is activated, the line of the central office line 1 is closed by its contact a1-1. When the office line 1 is closed, the calling signal stops, so the relay R1 is restored, the tone ringer signal is stopped by the contacts r and -2, and the amplifier ON information to each slave unit is added to the terminal 7 of the data selector IC 67. becomes OFF,
The 2Hz intermittent signal of the station line 1 lamp is A by contact r1-1.
Since it is blocked by the ND circuit 1C60, it becomes a continuous signal and the OR
The station line 1 lamp information becomes continuous lighting information through the circuit 1C64. The operation 0FF signal of the slave amplifier and the lighting information of the office line lamp are sent to the slave unit through the information line J, and all slave amplifiers are stopped, and the office line 1 lamp is turned on continuously.
The operation for terminating a call is the same as for calling a central office line. (
Operation of Holding and Reacquisition of Local Line) Next, the operation of holding and reacquisition after a call with the local line will be explained.

Assume that the caller presses the hold button while handset #1 is talking on the local line using central line 1.

When the hold button is pressed, the station line 1 button is not restored, and when the hold button is restored, the station line 1 button is also restored. The structure shall be such that Therefore, when the hold button is pressed, in addition to the current determining resistors R203 and R204 of the constant current circuit, a resistor R207 is added by the HK contact, so the current flowing through the resistor R207 is added to the normal call current. Resistor R207 so that this increase becomes about 20mA
Determine the value of Further, at this time, the HK contact short-circuits the telephone circuit TEL to prevent a voltage drop due to the telephone circuit TEL. The increased communication current is sent to the main device through the communication line, [communication line T#1 → resistor R4 → photocoupler PD1 →
SCR of S1 → transformer LTCO1 → resistor R8], and the voltage across resistor R8 increases. The comparator Comp6 detects this voltage increase, and its output turns on the transistor Tr7 to operate the H1 relay. When the H1 relay operates, the line is closed by the contact h1-1 and the resistor R42 due to the operation of the contact h1-1. If you release the hold button at this point, the station line 1 button will be restored along with the hold button, so the call current will disappear and the S1 S1 button will be restored.
CR turns OFF and the voltage across the resistor 8 disappears. When the voltage disappears, the comparators Comp4 and Comp6 are turned off. Comparator Co
A1 relay is restored by the output of mp4 and its contact a1-1
is closed. Also, the transistor Tr7 is turned off by the output of the comparator Comp6, but the H1 relay is connected to the contact h1.
-2 and contact a1-3, it is self-held and enters a suspended state.
When the A1 relay is restored and the H relay operates, contact h4-3
and a1-2, AND circuit 1C62 and OR circuit 1C
64 is turned on, the station line 1 lamp information changes from continuous information to a 1/2Hz intermittent signal, which is sent to each slave unit through the information line J, and the station line 1 lamp of each slave unit changes from continuous lighting to a 1/2Hz intermittent signal. Changes to 1/2Hz blinking. In this state, slave unit #1
presses the office line 1 button again, raises the handset, and goes to reacquire it, and the A1 relay operates in the same way as when making a call to the office line, and its contact a1-1 closes the line by transformer LTCO1. be done.

Also, H1 relay is restored by contact a1-3, and contacts h1-3 and a
Since AND circuit 1C62 and OR circuit 1C64 are turned off by 1-3 and a1-2, the station line 1 lamp information is 1/2H.
The Z intermittent signal changes to a continuous signal, and the station line 1 lamp of each slave unit changes from blinking to continuous lighting. Termination of the call is the same as for the central office line originating operation. (Extension call and extension call) When the extension button of handset #1 is pressed and the handset is raised, switch LK3 operates a constant current circuit with resistors R203 and R206, and a call current of 20 mA flows. (G) Wire P → Constant current circuit → Telephone circuit TEL →
The signal is sent to the main device through the path of switch LK3→switch LK2→switch LK1→hook switch HS→BS contact→talk line T#1].

In the main device, since the transistor Tr3 is ON, a voltage flows from the communication line T#1 to the transistor Tr3 and the resistor R3, and a voltage is generated across the resistor R3. This voltage operates comparator Comp3, and AND circuit 1C8
The signal is input to the AND circuit 1C35 through the gate. Also, when the extension transformer IT is not used, the extension detection circuit 3-2
No current flows through the resistor R39 inside the comparator Comp1.
6 is not operating, it is input to the AND circuit 1C35 through the NOT circuit 1C4] and the OR circuit 1C38. Therefore, the AND circuit 1C35 opens and triggers the gate of the SCR of S7 for coupling the handset #1 and the extension transformer IT, turning S7 ON. AND circuit 1C35
The outputs of 0R circuit 1C4, 0R circuit 1C2 and NO
It is added to the transistor Tr2 through the T circuit 1C3, and the transistor Tr2 is turned off and the transistor Tr3 is also turned off.
It becomes F. The communication current flowing through the transistor Tr3 and the resistor R3 is changed to the SCR of S7 when the transistor Tr3 is turned off.
is ON, so [Talking line T#1 → Resistor R4 → Photocoupler PD1 → SCR of S7 → Extension transformer IT → Resistor R3
9]. Since the communication current flows through the photocoupler PD1, the transistor Tr1 turns ON, and [NO
The transistors Tr2 and Tr3 are kept OFF through a path of T circuit 1C1→OR circuit 1C2→NOT circuit 1C3]. Since a communication current of 20 mA flows through the resistor R39, the voltage across the resistor R39 operates the comparator Comp16. The output of the comparator Comp16 turns on the extension lamp information, and this information is transferred to the parallel/serial conversion circuit 1.
4, the data is converted into information and sent to each slave unit via an information line J. Each slave unit has a comparator Comp201,C.
After the signal is separated into a synchronization pulse and an information pulse by the amp 202, it is converted into parallel information by the serial/parallel conversion circuit 23, and the transistor Tr204 is turned on through the resistor R212 and the Schmitt trigger IC207 to turn on the extension lamp. Next, when handset #1 is dialed for individual calling or simultaneous calling, the following operations occur.

(1) In the case of individual calling, when the call current is cut off by dialing, the "constant current circuit" on the handset side is connected to the resistor R2 by contact DP1.
06 is disconnected and the communication current is 7mA due to resistor R203.
Therefore, when the dial is connected, resistor R206 connects to contact DP1.
Since the terminals are connected by , a current of 20 mA, which is the same as the communication current, flows.

This intermittent current is sent to the main device through the communication line T#1, [communication line T#1 → resistor R4 → photocoupler PD1 → S7
A current flows through the path of SCR → extension transformer IT → resistor R39], and the voltage across the resistor R39 changes. Comparator Comp17 detects this, and [NOT circuit 1
C53→AND circuit 1C50→counter IC49] and is input to the decoder IC48. When the output corresponding to the dial is output to the decoder, if the output is ya 2, [AND circuit 1C46 → 0R circuit 1C43 → resistor R3
2 → Diode D4 → Extension transformer IT → Resistor R39]
A calling current flows through the path, and diode D4 turns on.
The state will be as follows. By turning on diode D4, slave unit #1
The audio signal is as follows: [Claim #1 → Call line T #1 → Capacitor C1 → SCR of S7 → Diode D4 → Capacitor C
9→Capacitor C4→Talking line T#2→Hook switch H
S → Capacitor C202 → AMP25 → Speaker 25]
The calling voice of slave unit #] is transmitted from the speaker 25 through the route. When the decoder IC48 outputs an output, the decoder output turns on the amplifier operation information through the OR circuit 1C52 and IC66. This information is sent to the slave units through the information line J, and operates the C relay to put the amplifier 24 of each slave unit into an operating state. Also, during the 1-output, the output of the decoder IC48 is sent to the trigger gate input of the cross point SCR for the extension of the slave unit called through the path of [AND circuit 1C64 → 0R circuit 1C43 → OR circuit IC39 → AND circuit 1C36]. Add High.

When handset #2 responds to the call, the call current 2 is determined by resistors R203 and R206 in the constant current circuit.
0mA is [power (G) wire P → constant current circuit → telephone circuit TEL → switch LK3 → switch LK2 → switch L
K1→Hook switch HS-+BS contact→Talking line T#2
] to the main device. Transistor Tr10 is O
Since it is in the N state, the communication current flows through the transistor Tr10.
Through the resistor R15, a voltage is generated across the resistor R15, and the comparator Comp9 operates. The output of comparator Comp9 is input to AND circuit 1C36 through AND circuit 1C21. Now, AND circuit 1C
Since a high signal is applied to the other input of 36 from the output of decoder IC48 through the path [AND circuit 1C46 → 0R circuit 1C43 → OR circuit 1C39], AND circuit 1C36 is opened and the connection between slave unit #2 and the extension transformer is applied. A trigger is applied to the SCR gate of S8 that connects IT, and S8 is turned ON. The output of AND circuit 1C36 is [
OR circuit 1C17 → 0R circuit 1C15 → NOT circuit 1C
16], the transistor Tr9 is turned off, and the transistor Tr10 is also turned off. When the transistor Tr10 is turned off and the SCR of S8 is turned on, the communication current flows through the path of [communication line T#2→resistor R16→phototransistor PD2→SCR of S8→extension transformer IT→resistance R39]. When the voltage across resistor R39 increases, comparator Comp18 operates and NOT
The output of the counter IC49 is reset through the circuit 1C51, and the output of the decoder IC48 is stopped. Therefore, the calling diode D4 is in the OFF state, and 0R
Since the output of the circuit 1C52 disappears, the amplifier operation information becomes 0FF.

Since the amplifier information was turned off on the slave unit, the C relay was restored.
The slave amplifier 24 stops. Here, handset #1 and handset #2
Since the SCRs of S7 and S8 are ON, they are connected by the extension transformer IT, and a mutual communication state is established.

When the call ends and handset #1 and handset #2 both put down their handsets, the call current disappears and the SCRs of S7 and S8 are restored.

When the SCRs of S7 and S8 are restored, the voltage across resistor R39 disappears, so comparators Comp16 and Com
p18 turns OFF, and comparator Comp16 turns OFF.
The extension lamp information is turned OFF by FF, and the extension lamps of each handset are turned off. (2) In the case of simultaneous calling, set the dial number for simultaneous calling to “0”, and use the decoder I
When the output of C48 is “0”, 0R circuit 1C42, IC
43, diode D3 for calling through IC44,
D4 and D5 are all turned on, and the calling voice from handset #1 is sent out to the communication lines of all handsets through diodes D3, D4, and D5, amplified by handset amplifier 24, and sent out from speaker 25.

In addition, the output "0" of the decoder IC48 adds High to the gate IC (AND circuit) input for triggering each SCR, and no matter which slave unit captures and responds to the extension, the communication path is connected to the extension transformer IT, and the slave unit is connected to the extension transformer IT. Establish a communication path with machine #1. When the communication path is established, the output of the decoder 1C48 disappears as in the case of an individual call, and the handsets other than those in the mutual communication state are disconnected from the extension transformer IT and placed in a confidential state. Termination of an extension call is the same as for an individual call.

Although the above example has been described in which two central office lines, one extension line, and three slave units are accommodated, the present invention is not limited to this example, and generally accommodates three or more central office lines and two extension lines. Of course, it can also be applied when accommodating more than 4 lines and 4 or more handsets, and depending on the number of lines and handsets required, the main device and the detection circuit and selection circuit in the telephone set may be required. This can be realized by making some changes.

As described above, in the button telephone device in which the talking current system is DC-separated from the central office line according to the present invention, each handset has a talking current that controls the current value of the talking current according to the selection operation of the button switch. In addition to being provided with a control means 21, the main device includes handset detection circuits 8-1 and 8- for identifying the current value of the communication current.
2, 8-3, and a plurality of Talos point thyristors 6-1, 6-2, and 7 for forming a communication path with each slave unit by the output of the slave unit detection circuit, and corresponding to each office line and extension line. a central office line or extension detection circuit 2-1-2, 2-2-2, 3-2 for monitoring the state of use of each trunk;
When an attempt is made to capture a central office line or extension that is already being used for a call, the output of the central office line or extension detection circuit prevents the triggering of the cross-point thyristor even if the handset detection circuit outputs. However, it is possible to realize a confidential communication system in a button telephone device, which is characterized in that it is configured to create a confidential state by preventing the connection of a trunk that is already in use with a handset that newly attempts to interrupt.

As explained in detail above, according to the present invention, by providing the cross-point thyristor circuit in the main device with a secret function, the overall configuration becomes simple and inexpensive, and de-encryption can be easily performed. There is a potential effect.

[Brief explanation of the drawing]

FIG. 1 is a waveform diagram for explaining the transmission of dial pulses in the button telephone device according to the present invention, FIG. 2 is a waveform diagram for explaining the transmission of information in the button telephone device according to the present invention, and FIG. FIG. 3 is a block diagram showing the main configuration of the button telephone device according to the present invention, and FIGS. 4 and 5 are circuit diagrams of the main device and the telephone, showing detailed circuit configuration examples of the button telephone device according to the present invention. .

Claims (1)

[Claims] 1. In a button telephone device in which the communication current system is DC-separated from the central office line, each handset is provided with communication current control means for controlling the current value of the communication current according to button selection operations, and the main device includes a handset detection circuit that identifies the current value of the communication current, a plurality of cross-point thyristors for forming a communication path with each handset using the output of the handset detection circuit, and a telephone line for each office line and extension line. It is equipped with a central office line or extension detection circuit that monitors the usage status of each corresponding trunk, and when an attempt is made to capture a central office line or extension that is already being used for a call, the output of the central office line or extension detection circuit is used. Even if there is an output from the handset detection circuit, triggering of the cross-point thyristor is prohibited, and a confidential state is established by preventing the connection of the trunk that is already in use with the handset that newly attempts to interrupt. A confidential communication method in a button telephone device, characterized in that it is configured as follows.