JP2008028866A - Intercom device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve optimum controlled communication without lowering voice impedance of a communication line even if a switching circuit is not provided in the communication line and between AM transmission circuits. <P>SOLUTION: An intercom device 1, which superimposedly outputs power from a power supply circuit 23 to the communication line 30 for transferring speech voice between an entrance slave unit 10 and an indoor master unit 20A is provided with; a master unit side voice impedance increase circuit 24 including a PNP transistor 31 connecting a collector 31A to the communication line, and an emitter 31B to the power supply circuit through an emitter resistor 32; a first resistor 33 connected between the collector 31A and a base 31C; a second resistor 34 connected between the base and the power supply circuit; and a first capacitor 35 connected in parallel to the second resistor. Output from a master-side controlled communication circuit 22 superimposedly outputting a control signal through the communication line is connected to the emitter of the PNP transistor. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an intercom apparatus that performs power feeding, voice communication, and control communication using two communication lines between an indoor parent device and an entrance child device.

  Conventionally, such an intercom device uses a two-wire communication line between an indoor parent device and an entrance child device, for example, when power is supplied from the power supply circuit inside the indoor parent device to the entrance child device. When performing the power supply operation to the entrance cordless handset with the DC voltage of the power supply circuit through and performing voice communication between the indoor base unit and the entrance cordless handset, the voice is heard in the audible frequency band of several tens Hz to several kHz through the communication line. The communication is executed.

  Furthermore, according to the intercom device, when executing control communication such as switching of the operation state using the communication line between the indoor parent device and the entrance child device, for example, several tens kHz exceeding the audible frequency band through the communication line. Control communication is performed using the AM signal in the above frequency band.

  FIG. 6 is a block diagram showing a schematic configuration inside a conventional intercom apparatus.

  The intercom apparatus 100 shown in FIG. 6 includes a two-wire communication connection between the entrance slave unit 10 arranged outside the entrance room, the indoor master unit 20 arranged indoors, and the indoor master unit 20 and the entrance slave unit 10. The indoor parent device 20 performs a power feeding operation to the entrance slave device 10 through the communication line 30, and the indoor parent device 20 and the entrance slave device 10 use the communication line 30. Voice communication and control communication are executed.

  The indoor parent device 20 executes control communication with the front door slave device 10 using the master side voice circuit 21 that performs voice communication with the front door slave device 10 and an AM signal in a frequency band that exceeds the audible frequency band. Base unit side control communication circuit 22, power source circuit 23 for supplying power to intercom apparatus 100 as a whole, base unit side audio impedance up circuit 24 for increasing audio impedance in the audible frequency band of communication line 30, and indoor base unit 20 And a base unit side control circuit 25 for controlling the whole.

  The base unit side audio impedance up circuit 24 has a PNP transistor 31 that connects the collector 31A to the communication line 30 and connects the emitter 31B to the power circuit 23 inside the indoor base unit 20 via the emitter resistor 32, and the PNP transistor 31. The first bias resistor 33 connected between the collector 31A and the base 31C, the second bias resistor 34 connected between the base 31C of the PNP transistor 31 and the power supply circuit 23, and the second bias resistor 34 connected in parallel. And the first capacitor 35 formed.

  Since the base voltage does not fluctuate due to the operation of the first capacitor 35, the base voltage does not fluctuate due to the operation of the first capacitor 35, the AC current of the collector becomes constant and the ac voltage increases. However, the alternating current does not increase, that is, the voice impedance is increased as viewed from the communication line 30.

  The base-side audio impedance up circuit 24 increases the audio impedance so that the output signal of the base-side audio circuit 21 connected to the communication line 30 is not absorbed by the power supply circuit 23 side. The output signal 21 is transmitted to the front door 10 through the communication line 30.

  If the base-side audio impedance up circuit 24 is not arranged between the communication line 30 and the power supply circuit 23, the output signal of the base-side audio circuit 21 connected to the communication line 30 is absorbed by the power supply circuit 23 side. As a result, the output signal cannot be transmitted to the front door 10.

  The master-side control communication circuit 22 is connected to the master-side output resistor 22A and the master-side output resistor 22A. The control content to the entrance slave unit 10 is AM-modulated and AM is sent to the entrance slave unit 10 side. AM demodulating the AM signal from the main unit side AM transmission circuit 22B that outputs as a signal, the main unit side switch circuit 22C that turns ON / OFF the connection between the communication line 30 and the main unit side output resistor 22A Thus, the master unit AM receiving circuit 22D for receiving the control content from the entrance slave unit 10 and the master unit side receiving impedance 22E connected to the master unit AM receiving circuit 22D are provided.

  Further, when the master unit side switch circuit 22C in the master unit side control communication circuit 22 outputs an AM signal from the master unit side AM transmission circuit 22B to the entrance slave unit 10, the communication line 30 and the master unit side output resistance The connection between 22A is turned on. In the parent AM transmission circuit 22B, in order to keep the AM signal output level at a predetermined level or higher, the transmission impedance on the parent AM transmission circuit 22B side is lowered to increase the output level. Yes.

  When the master unit side switch circuit 22C does not output an AM signal from the master unit side AM transmitter circuit 22B to the entrance slave unit 10, the connection between the communication line 30 and the master unit side output resistor 22A is turned off. The transmission impedance on the machine-side AM transmission circuit 22B side is prevented from absorbing the output signal of the parent machine-side audio circuit 21 on the communication line 30.

  Further, the entrance handset 10 performs control communication with the indoor base unit 20 using the handset side audio circuit 11 that performs voice communication with the indoor base unit 20 and an AM signal in a frequency band that exceeds the audible frequency band. The main unit side control communication circuit 12 to be executed, the sub unit side audio impedance increase circuit 13 that increases the audio impedance of the communication line 30, the load circuit 14 that feeds power from the indoor main unit 20, and the entire front unit 10 are controlled. And a slave unit side control circuit 15.

  Further, the handset side voice impedance up circuit 13 connects the collector 41A to the communication line 30, and connects the emitter 41B to the load circuit 14 in the entrance handset 10 through the emitter resistor 42, and this NPN transistor. A third bias resistor 43 connected between the collector 41A and the base 41C of the transistor 41, a fourth bias resistor 44 connected between the base 41C of the NPN transistor 41 and the load circuit 14, and the fourth bias resistor 44 in parallel. And a second capacitor 45 connected to the.

  Since the base voltage does not fluctuate even if the load state on the collector side fluctuates due to the operation of the second capacitor 45, the cordless handset-side audio impedance up circuit 13 has a constant ac current in the collector and the ac voltage increases. However, the alternating current does not increase, that is, the voice impedance is increased as viewed from the communication line 30.

  And the subunit | mobile_unit side audio | voice impedance up circuit 13 raises audio | voice impedance, the output signal of the subunit | mobile_unit side audio | voice circuit 11 connected to the communication line 30 is not absorbed by the load circuit 14 side, but a subunit | mobile_unit side audio | voice The output signal of the circuit 11 is transmitted to the indoor parent device 20 through the communication line 30.

  If the handset side voice impedance up circuit 13 is not arranged between the communication line 30 and the load circuit 14, the output signal of the handset side voice circuit 11 connected to the communication line 30 is absorbed by the load circuit 14 side. As a result, the output signal cannot be transmitted to the indoor base unit 20.

  The slave unit side control communication circuit 12 is connected to the slave unit side output resistor 12A and this slave unit side output resistor 12A, and AM control is performed on the control content to the indoor master unit 20, and an AM signal is sent to the indoor master unit 20 side. The AM signal from the child machine side AM transmitter circuit 12B to output, the child machine side switch circuit 12C for turning ON / OFF the connection between the communication line 30 and the parent machine side output resistor 12B, and the AM signal from the indoor parent machine 20 are subjected to AM demodulation. A slave unit AM receiving circuit 12D that receives control content from the indoor master unit 20 and a slave unit side reception impedance 12E connected to the slave unit AM receiving circuit 12D are provided.

  When the slave unit side switch circuit 12C outputs an AM signal from the slave unit side AM transmitter circuit 12B to the indoor master unit 20, the slave unit side switch circuit 12C turns on the connection between the communication line 30 and the slave unit side output resistor 12A. In order to keep the output level of the signal above a predetermined level, the transmission impedance of the slave AM transmission circuit 12B is lowered to increase the output level.

  When the slave unit side switch circuit 12C does not output an AM signal from the slave unit side AM transmitter circuit 12B to the indoor master unit 20, the slave unit side switch circuit 12C turns off the connection between the communication line 30 and the slave unit side output resistor 12A. The transmission impedance on the machine-side AM transmission circuit 12B side is prevented from absorbing the output signal of the child machine-side audio circuit 11 on the communication line 30.

  Therefore, according to such a conventional intercom device 100, for example, when an AM signal is output from the parent device side AM transmission circuit 22B (slave device side AM transmission circuit 12B) to the entrance child device 10 (indoor master device 20), Communication is performed through the master unit side switch circuit 22C (slave unit side switch circuit 12C) in a state where the transmission impedance of the base unit side AM transmitter circuit 22B (slave unit side AM transmitter circuit 12B) is lowered and the output level of the AM signal is increased. By connecting the line 30 and the master unit side output resistor 22A (slave unit side output resistor 12A), the master unit side AM transmitter circuit 22B (slave unit side AM transmitter circuit 12B) is connected to the entrance slave unit 10 (indoor master unit 20). Since the AM signal is output to the control signal, highly reliable control communication can be realized.

  Furthermore, according to the conventional intercom apparatus 100, when the AM signal is not output from the base-unit-side AM transmission circuit 22B (slave-unit-side AM transmission circuit 12B) to the entrance slave unit 10 (indoor master unit 20), the base-unit-side switch circuit Since the connection between the communication line 30 and the master unit side output resistor 22A (slave unit output resistor 12A) is disconnected (OFF) through 22C (slave unit side switch circuit 12C), the master unit side AM transmitter circuit 22B ( The influence of the transmission impedance of the slave unit side AM transmitter circuit 12B) is eliminated, and the output signal of the master unit side voice circuit 21 (slave unit side voice circuit 11) becomes the master unit side AM transmitter circuit 22B (slave unit side AM transmitter circuit 12B). Can be prevented from being absorbed by the transmission impedance.

Although the applicant has not been able to find the prior document of the conventional intercom apparatus shown in FIG. 6, for example, the bus line and the transmission circuit are connected when data is transmitted, and the bus line and the transmission circuit are received when data is received. A technology for realizing a good signal transmission by providing a switching function for cutting off the connection to the bus line and preventing a decrease in impedance viewed from the bus line side is widely known (see, for example, Patent Document 1).
JP-A-7-231324 (see abstract and FIG. 1)

  However, according to the conventional intercom device 100, when an AM signal is not output from the parent device side AM transmission circuit 22B (child device side AM transmission circuit 12B) to the front child device 10 (indoor master device 20), The master unit side audio circuit 21 (slave unit side) is disconnected by cutting the connection between the master unit side output resistor 22A (slave unit side output resistor 12A) and the communication line 30 through the unit side switch circuit 22C (slave unit side switch circuit 12C). The output signal from the audio circuit 11) is not absorbed by the transmission impedance of the parent machine AM transmission circuit 22B (child machine AM transmission circuit 12B), but the communication line 30 and the parent machine output resistor 22A (child machine side) It is necessary to dispose the master unit side switch circuit 22C (slave unit side switch circuit 12C) between the output resistors 12A).

  The present invention has been made in view of the above points, and an object of the present invention is to provide an interphone capable of realizing optimal control communication without reducing a voice impedance of a communication line without providing a switch circuit. To provide an apparatus.

  In order to achieve the above object, an interphone apparatus according to the present invention is an intercom apparatus that superimposes and outputs power from a power supply circuit on a communication line that transmits a call voice between an entrance cordless handset and an indoor base phone. A PNP transistor connected to the power supply circuit via an emitter resistor, a first resistor connected between the collector and base of the PNP transistor, the base of the PNP transistor, and the power supply circuit A first audio impedance up circuit having a second resistor connected between the first resistor and a first capacitor connected in parallel to the second resistor, and a control signal superimposed on the emitter of the PNP transistor through the communication line The output of the communication circuit was connected.

  In order to achieve the above object, an interphone apparatus of the present invention is an interphone apparatus that superimposes and outputs a power supply from a power supply circuit on a communication line that transmits a call voice between an entrance cordless handset and an indoor base phone. An NPN transistor having a collector connected to a communication line and an emitter connected to a load circuit via an emitter resistor, a third resistor connected between the collector and base of the NPN transistor, the base and load of the NPN transistor A second audio impedance-up circuit having a fourth resistor connected between the circuits and a second capacitor connected in parallel to the fourth resistor, and outputting a control signal superimposed on the emitter of the NPN transistor through the communication line; The output of the control communication circuit was connected.

  According to the intercom apparatus of the present invention configured as described above, the output of the control communication circuit that superimposes and outputs the control signal through the communication line is connected to the emitter of the PNP transistor of the first impedance up circuit. Even if the control communication circuit impedance is lowered and the output level of the control signal is increased, the impedance of the control communication circuit is not connected between the communication lines between the entrance slave unit and the indoor master unit. It is not necessary to provide a switch circuit, and it is possible to reliably prevent the loss of the audio signal on the communication line as a result of reliably preventing the voice impedance on the communication line from being lowered. Can be realized.

  Further, according to the intercom apparatus of the present invention, the output of the control communication circuit that superimposes and outputs the control signal through the communication line is connected to the emitter of the NPN transistor of the second impedance up circuit. Even if the output level of the control signal is increased by lowering the impedance, the impedance of the control communication circuit is not connected between the communication lines between the entrance unit and the indoor unit. As a result, it is possible to reliably prevent the loss of the audio signal on the communication line and to realize highly reliable control communication. it can.

  The intercom apparatus according to claim 1 is an intercom apparatus that superimposes and outputs a power supply from a power supply circuit on a communication line that transmits a call voice between an entrance slave unit and an indoor master unit, and a collector is connected to the communication line And a PNP transistor for connecting an emitter to the power supply circuit via an emitter resistor, a first resistor connected between the collector and base of the PNP transistor, and a connection between the base and power supply circuit of the PNP transistor. An output of a control communication circuit comprising a first voice impedance up circuit having a second resistor and a first capacitor connected in parallel to the second resistor, and outputting a control signal superimposed on the emitter of the PNP transistor through the communication line Was connected.

  Therefore, according to the interphone device of claim 1, the output of the control communication circuit that superimposes and outputs the control signal through the communication line is connected to the emitter of the PNP transistor of the first impedance up circuit. Even if the output level of the control signal is increased by lowering the impedance of the control communication circuit, it is possible to reliably prevent the voice impedance on the communication line from being lowered without providing a switch circuit as in the prior art. Loss of the audio signal on the line can be surely prevented.

  Furthermore, according to the intercom apparatus according to claim 1, the output of the control communication circuit that superimposes and outputs the control signal through the communication line is connected to the emitter of the PNP transistor of the first impedance up circuit. By amplifying the output level of the control signal from the control communication circuit using the base-grounded amplifier characteristics of the transistor, the reliability of the control communication can be greatly improved.

  Further, in the interphone device according to claim 2 of the present application, in addition to the configuration according to claim 1 of the present application, a constant voltage circuit is connected instead of the first capacitor and the second resistor.

  Therefore, according to the intercom device according to claim 2 of the present application, in addition to the effect of claim 1 of the present application, instead of the first capacitor and the second resistor, a constant voltage circuit such as a Zener diode is used. As a result, the base voltage is constant in terms of direct current, the impedance of the communication line at a lower frequency can be increased, and signal transmission at a low frequency can be made possible.

  Further, in the intercom apparatus according to claim 3 of the present application, in addition to the configuration according to claim 1 or 2, the PNP transistor is configured by Darlington connection.

  Therefore, according to the intercom device according to claim 3 of the present application, in addition to the effect of claim 1 or 2 of the present application, the PNP transistor is configured by Darlington connection, thereby improving the impedance increase performance of the communication line. And stable signal transmission is possible.

  The intercom apparatus according to claim 4 is an intercom apparatus that outputs a power supply from a power supply circuit superimposed on a communication line that transmits a call voice between an entrance cordless handset and an indoor base phone. And an NPN transistor for connecting the emitter to the load circuit via an emitter resistor, a third resistor connected between the collector and base of the NPN transistor, and a connection between the base and load circuit of the NPN transistor And a second voice impedance-up circuit having a second resistor connected in parallel to the fourth resistor, and a control communication circuit that outputs a control signal superimposed on the emitter of the NPN transistor through the communication line. The output was connected.

  Therefore, according to the interphone device according to claim 4 of the present application, the output of the control communication circuit that superimposes and outputs the control signal through the communication line is connected to the emitter of the NPN transistor of the second impedance up circuit. Even if the output level of the control signal is increased by lowering the impedance of the control communication circuit, it is possible to reliably prevent the voice impedance on the communication line from being lowered without providing a switch circuit as in the prior art. Loss of audio signals on the communication line can be reliably prevented.

  Furthermore, according to the interphone device of claim 4, the output of the control communication circuit that superimposes and outputs the control signal through the communication line is connected to the emitter of the NPN transistor of the second impedance up circuit. By amplifying the output level of the control signal from the control communication circuit using the base-grounded amplifier characteristics of the transistor, the reliability of the control communication can be greatly improved.

  Further, in the intercom apparatus according to claim 5 of the present application, in addition to the configuration of claim 4 of the present application, a constant voltage circuit is connected instead of the second capacitor and the fourth resistor.

  Therefore, according to the intercom device according to claim 5 of the present application, in addition to the effect of claim 4 of the present application, instead of the second capacitor and the fourth resistor, a constant voltage circuit such as a Zener diode is used. As a result, the base voltage is constant in terms of direct current, the impedance of the communication line at a lower frequency can be increased, and signal transmission at a low frequency can be made possible.

  Further, in the intercom apparatus according to claim 6 of the present application, in addition to the configuration of claim 4 or 5 of the present application, the NPN transistor is configured by Darlington connection.

  Therefore, according to the intercom device according to claim 6 of the present application, in addition to the effect of claim 4 or 5 of the present application, the NPN transistor is configured by Darlington connection, so that the impedance increase performance of the communication line is improved. And stable signal transmission is possible.

  Hereinafter, an intercom apparatus showing an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a schematic configuration inside an intercom apparatus showing a first embodiment of the present invention. The same components as those of the intercom apparatus shown in FIG. 6 are denoted by the same reference numerals, and the description of the overlapping components and operations is omitted.

  The interphone device 1 shown in FIG. 1 and the interphone device 100 shown in FIG. 6 are different from each other in that the base unit side AM transmission circuit is not provided with the base unit side switch circuit 22C between the communication line 30 and the base unit side output resistor 22A. The indoor base unit 20A includes a base unit side control communication circuit 50 configured to connect the base unit side output resistance 22A of 22B to the emitter 31B of the PNP transistor 31 in the base unit side audio impedance up circuit 24.

  The PNP transistor 31 amplifies and outputs the AM signal using the grounded base amplifier characteristic when the AM signal from the parent AM transmission circuit 22B is input to the emitter 31B through the parent output resistor 22A.

  The interphone apparatus according to claim 1 of the present application is the interphone apparatus 1, the PNP transistor is the PNP transistor 31, the emitter resistance is the emitter resistance 32, the first resistance is the first bias resistance 33, the second resistance is the second bias resistance 34, One capacitor corresponds to the first capacitor 35, the first audio impedance increase circuit corresponds to the parent device side audio impedance increase circuit 24, and the control communication circuit corresponds to the parent device side AM transmission circuit 22B and the parent device side output resistor 22A.

  Next, the operation of the intercom apparatus 1 showing the first embodiment will be described.

  When the base station side AM communication circuit 22B of the base unit side control communication circuit 50 outputs an AM signal to the entrance slave unit 10, the PNP transistor inside the base unit side voice impedance up circuit 24 through the base unit side output resistor 22A. The AM signal is input to the emitter 31B side of the 31.

  The PNP transistor 31 amplifies the AM signal based on the characteristics of the grounded base amplifier, and supplies the amplified AM signal to the slave unit side AM reception circuit 12D on the entrance slave unit 10 side through the communication line 30.

  FIG. 2 is an operation explanatory view briefly showing the function of the grounded base amplifier characteristic of the base unit side voice impedance up circuit 24 which is the main part of the intercom apparatus 1 showing the first embodiment.

  The output voltage VO of the parent device AM transmission circuit 22B shown in FIG. 2 is input to the emitter 31B side of the PNP transistor 31 via the parent device output resistor RO. At this time, since the emitter voltage VE is a difference between the base voltage VB and the base-emitter voltage VBE, it can be expressed by VE = VB−VBE. The base-emitter voltage VBE is normally a fixed value of 0.6 to 0.7 V in the case of a silicon transistor.

  The base voltage VB is a current value IO that is input to the emitter 31B from the base-side AM transmission circuit 22B through the output resistor RO according to the operation of the first capacitor 35, as IO = (VO−VE) / RO. Can be represented.

  Further, since the current value IE flowing through the emitter resistor 32 varies according to the variation of the current value IO, the variation amount IOIO of the current IO and the variation amount ΔIE of the current value IE are ΔIO = ΔIE.

  Since the base current of the PNP transistor 31 is sufficiently smaller than the collector current and the emitter current, the change amount ΔIZ of the collector current, that is, the load current IZ is ΔIZ≈ΔIE = ΔIO. At this time, the change amount ΔVSIG of the collector voltage VSIG which is the signal voltage of the communication line 30 is ΔVSIG = ΔIZ * RZ = Δ (VO−VE) * RZ / RO, and therefore the amplification factor is an amplifier of RZ / RO. .

  In other words, the PNP transistor 31 of the base unit side voice impedance up circuit 24 amplifies the AM signal from the base unit side AM transmission circuit 22B using this base ground amplifier characteristic and transmits it to the entrance slave unit 10 through the communication line 30. Output.

  Further, when the indoor master unit 20A receives an AM signal from the entrance slave unit 10, the collector voltage of the PNP transistor 31 varies, but even if the collector voltage varies, the base voltage VBE varies due to the function of the first capacitor 35. Therefore, the current flowing from the power supply circuit 23 does not fluctuate, and the value of the impedance Z of the communication line 30 can be reduced by reducing the denominator current I in the equation expressed by Z = V / I. As a result, the state where the impedance Z is high can be maintained.

  Therefore, according to the first embodiment, the base-side output resistor 22A of the base-side AM transmission circuit 22B is connected to the emitter 31B side of the PNP transistor 31 inside the base-side audio impedance up circuit 24. Therefore, even if the impedance of the parent AM transmission circuit 22B is lowered and the output level of the AM signal is increased, the switch circuit (master switch circuit 22C) as in the prior art is not provided, and the communication line 30 is provided. As a result, the loss of the audio signal on the communication line 30 can be reliably prevented by reliably preventing the voice impedance from being lowered.

  Further, according to the first embodiment, the base-side output resistor 22A of the base-side AM transmission circuit 22B is connected to the emitter 31B side of the PNP transistor 31 in the base-side audio impedance up circuit 24. Therefore, the reliability of the control communication can be greatly improved by amplifying the output level of the AM signal from the parent AM transmission circuit 22B using the base-grounded amplifier characteristic of the PNP transistor 31.

(Embodiment 2)
FIG. 3 is a block diagram showing a schematic configuration inside the intercom apparatus according to the second embodiment. The same components as those of the intercom apparatus shown in FIG. 6 are denoted by the same reference numerals, and the description of the overlapping components and operations is omitted.

  The interphone device 1A shown in FIG. 3 is different from the interphone device 100 shown in FIG. 6 in that the handset side AM transmission circuit 12B is provided without providing the handset side switch circuit 12C between the communication line 30 and the handset side output resistor 12A. It is in the entrance cordless handset 10A provided with the handset side control communication circuit 60 that connects the handset side output resistance 12A to the emitter 41B of the NPN transistor 41 in the handset side voice impedance up circuit 13.

  The NPN transistor 41 amplifies and outputs the AM signal using the grounded base amplifier characteristic when the AM signal from the slave side AM transmission circuit 12B is input to the emitter 41A side through the slave side output resistor 12A.

  The interphone device according to claim 4 of the present application is the interphone device 1A, the PNP transistor is the PNP transistor 41, the emitter resistor is the emitter resistor 42, the third resistor is the third bias resistor 43, the fourth resistor is the fourth bias resistor 44, The second capacitor 45 corresponds to the second capacitor 45, the second voice impedance up circuit corresponds to the handset side voice impedance up circuit 13, and the control communication circuit corresponds to the handset side AM transmission circuit 12B and the handset side output resistor 12A.

  Next, the operation of the intercom apparatus 1A showing the second embodiment will be described.

  When the slave unit side AM communication circuit 12B of the slave unit side control communication circuit 60 outputs an AM signal to the indoor master unit 20, the NPN transistor in the slave unit side voice impedance up circuit 13 is passed through the slave unit side output resistor 12A. The AM signal is input to the emitter 41A side of 41.

  The NPN transistor 41 amplifies the AM signal based on the grounded base amplifier characteristic, and supplies the amplified AM signal to the parent device side AM receiving circuit 22D on the indoor parent device 20 side through the communication line 30.

  Therefore, according to the second embodiment, the handset side output resistor 12A of the handset side AM transmitter circuit 12B is connected to the emitter 41B side of the NPN transistor 41 in the handset side voice impedance up circuit 13. Therefore, even if the impedance of the AM transmitter circuit 12B on the slave unit is lowered and the output level of the AM signal is increased, the switch circuit (slave unit switch circuit 12C) as in the prior art is not provided and the communication line 30 is provided. As a result, the loss of the audio signal on the communication line 30 can be reliably prevented by reliably preventing the voice impedance from being lowered.

  Further, according to the second embodiment, the handset side output resistor 12A of the handset side AM transmission circuit 12B is connected to the emitter 41B side of the NPN transistor 41 in the handset side voice impedance up circuit 13. Therefore, the reliability of control communication can be greatly improved by amplifying the output level of the AM signal from the parent AM transmission circuit 12B using the base ground amplifier characteristics of the NPN transistor 41.

(Embodiment 3)
FIG. 4 is a block diagram showing a schematic configuration inside the audio impedance up circuit 24 (13), which is a main part of the intercom apparatus 1 showing the third embodiment.

  4A, the base-side audio impedance up circuit 24 is energized instead of the second bias resistor 34 and the first capacitor 35 inside the base-side audio impedance up circuit 24 shown in FIG. 1 (FIG. 3). A first Zener diode 71 is disposed as a constant voltage element whose voltage is fixed regardless of the current, and the base voltage of the PNP transistor 31 is fixed in accordance with the operation of the first Zener diode 71 to establish a communication line 30. As a result, the output signal of the main unit side audio circuit 11 connected to the communication line 30 is not absorbed by the power supply circuit 23 side, and the output signal of the main unit side audio circuit 21 is transmitted through the communication line 30. It can be transmitted to the entrance unit 10 (10A).

  Further, the handset side voice impedance up circuit 13 shown in FIG. 4B is replaced with the fourth bias resistor 44 and the second capacitor 45 inside the handset side voice impedance up circuit 13 shown in FIG. 1 (FIG. 3). By arranging the second Zener diode 72 as a constant voltage element and fixing the base voltage of the NPN transistor 61 according to the operation of the second Zener diode 71, the voice impedance viewed from the communication line 30 is increased. The output signal of the handset side audio circuit 21 connected to the communication line 30 can be transmitted to the indoor base unit 20A (20) through the communication line 30.

  The constant voltage circuit according to claim 2 corresponds to the first Zener diode 71, and the constant voltage circuit according to claim 5 corresponds to the second Zener diode 72.

  Therefore, according to the third embodiment, as shown in FIG. 4A, instead of the first capacitor 35 and the second bias resistor 34, the first Zener diode 71 is used. The voltage becomes constant even in direct current, the impedance of the communication line at a lower frequency can be increased, and signal transmission at a low frequency can be achieved.

  Further, according to the third embodiment, since the second Zener diode 72 is used instead of the second capacitor 45 and the fourth bias resistor 44 as shown in FIG. The voltage becomes constant even in direct current, the impedance of the communication line at a lower frequency can be increased, and signal transmission at a low frequency can be achieved.

(Embodiment 4)
FIG. 5 is a block diagram showing a schematic configuration inside the voice impedance up circuit 24 (13) inside the intercom apparatus showing the fourth embodiment.

  In the base unit side voice impedance up circuit 24 shown in FIG. 5A, a Darlington circuit 73 is arranged instead of the PNP transistor 31 in the base unit side voice impedance up circuit 24 shown in FIG. 1 (FIG. 3). Is.

  Similarly, the handset side voice impedance up circuit 13 shown in FIG. 5B includes a Darlington circuit 74 instead of the NPN transistor 41 in the handset side voice impedance up circuit 13 shown in FIG. 1 (FIG. 3). It is what you do.

  The PNP transistor according to claim 3 corresponds to the Darlington circuit 73, and the NPN transistor according to claim 6 corresponds to the Darlington circuit 74.

  Therefore, according to the fourth embodiment, the Darlington circuit 73 is arranged instead of the PNP transistor 31 in the base-side voice impedance up circuit 24 as shown in FIG. The impedance up performance can be improved, and stable signal transmission is possible.

  Further, according to the fourth embodiment, as shown in FIG. 5B, the Darlington circuit 74 is arranged instead of the NPN transistor 41 in the handset side voice impedance up circuit 13, so that the communication line The impedance up performance can be improved, and stable signal transmission is possible.

  According to the intercom device of the present invention configured as described above, the output of the control communication circuit that outputs the control signal through the communication line is connected to the emitter of the PNP transistor of the first impedance up circuit. Even if the output level of the control signal is increased by lowering the impedance of the control communication circuit, it is possible to reliably prevent the voice impedance on the communication line from being lowered without providing a switch circuit as in the prior art. Since loss of the audio signal on the line can be surely prevented, it is useful for an in-house intercom device, for example.

The block diagram which shows schematic structure inside the intercom apparatus which shows the 1st Embodiment of this invention. Operation explanatory diagram briefly showing the function of the base-grounded amplifier characteristic of the base-side audio impedance up circuit according to the first embodiment The block diagram which shows schematic structure inside the intercom apparatus which shows the 2nd Embodiment of this invention. The block diagram which shows the schematic structure inside the audio | voice impedance increase circuit inside the intercom apparatus which shows the 3rd Embodiment of this invention. (A) Base unit side audio | voice impedance increase circuit (b) Slave unit side audio | voice impedance increase circuit The block diagram which shows schematic structure inside the audio | voice impedance increase circuit inside the intercom apparatus which shows the 4th Embodiment of this invention. (A) Base unit side audio | voice impedance increase circuit (b) Slave unit side audio | voice impedance increase circuit The block diagram which shows schematic structure inside the intercom apparatus of a prior art

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Interphone apparatus 1A Interphone apparatus 10 Entrance cordless handset 10A Entrance cordless handset 13 Cordless handset side voice impedance up circuit (2nd voice impedance up circuit)
14 Load Circuit 20 Indoor Master Unit 20A Indoor Master Unit 23 Power Supply Circuit 24 Parent Unit Side Voice Impedance Circuit (First Audio Impedance Circuit)
30 Communication line 31 PNP transistor 32 Emitter resistance 33 First bias resistance (first resistance)
34 Second bias resistor (second resistor)
35 First capacitor 41 NPN transistor 42 Emitter resistance 43 Third bias resistance (third resistance)
44 4th bias resistor (4th resistor)
45 Second capacitor 71 First Zener diode (constant voltage circuit)
72 Second Zener Diode (Constant Voltage Circuit)
73 Darlington Circuit 74 Darlington Circuit

Claims (6)

An intercom device that superimposes and outputs a power supply from a power supply circuit on a communication line that transmits call voice between an entrance cordless handset and an indoor base phone,
A PNP transistor connecting a collector to the communication line and connecting an emitter to the power supply circuit via an emitter resistor, a first resistor connected between the collector and base of the PNP transistor, the base of the PNP transistor, and A first audio impedance up circuit having a second resistor connected between the power supply circuits and a first capacitor connected in parallel to the second resistor;
An intercom apparatus, wherein an output of a control communication circuit that superimposes and outputs a control signal through the communication line is connected to an emitter of the PNP transistor.   The intercom apparatus according to claim 1, wherein a constant voltage circuit is connected instead of the first capacitor and the second resistor.   3. The intercom apparatus according to claim 1, wherein the PNP transistor is configured by Darlington connection. An intercom device that superimposes and outputs a power supply from a power supply circuit on a communication line that transmits call voice between an entrance cordless handset and an indoor base phone,
An NPN transistor for connecting a collector to the communication line and connecting an emitter to a load circuit via an emitter resistor, a third resistor connected between the collector and base of the NPN transistor, the base of the NPN transistor, and the base A second audio impedance increasing circuit having a fourth resistor connected between the load circuits and a second capacitor connected in parallel to the fourth resistor;
An intercom apparatus, wherein an output of a control communication circuit that superimposes and outputs a control signal through the communication line is connected to an emitter of the NPN transistor.   The intercom apparatus according to claim 4, wherein a constant voltage circuit is connected instead of the second capacitor and the fourth resistor. 6. The intercom apparatus according to claim 4, wherein the NPN transistor is configured by Darlington connection.

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