JP2005159890A - Intercom system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce electric power consumption of an intercom system and to extend its communication range by ensuring a low level of voltage of a power supply which is set by at least one entrance slave unit with a camera, a master unit with a monitor, and at least one additional master unit with a monitor, and by reducing the burden of power supply. <P>SOLUTION: One or more entrance slave units 1a and 1b, a master unit 2 and one or more additional master units 3a and 3b respectively have slave unit speakers 13a and 13b, a master unit speaker 20 and additional master unit speakers 30a and 30b and are respectively equipped with power amplifiers 103a, 103b, 202, 302a and 302b for driving the corresponding speakers. In this case, class D amplifiers using either of PWM and ΣΔ modulation methods which exhibit a high electric power conversion efficiency and a low power loss due to generation of heat, are used. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an interphone device, and more particularly to an interphone device in which power saving and communication communication distance are extended.

  Conventionally, an interphone device shown in the system configuration diagram of FIG. 5 has been proposed as this type of interphone device.

  The intercom apparatus shown in the system configuration diagram of FIG. 5 has at least one, in this case, two entrance slave units 501a and 501b with a camera, and a master unit 502 with a monitor or a monitor with (separate) two-wire cables L501a and L501b. At least one, in this case, two additional base units with monitors 503a and 503b are connected via a base unit 502 by two-wire cables L502a and L502b. In addition, the (two) camera-equipped slave units 501a and 501b are installed at different locations in the entrance of the dwelling unit, and have the same configuration. ) 512a, 512b, and speakers (hereinafter referred to as slave unit speakers) 513a, 513b. The monitor-equipped parent device 502 is installed in a dwelling unit, and includes a speaker (hereinafter referred to as a parent device speaker) 520, a microphone (hereinafter referred to as a parent device microphone) 521, a call button (hereinafter referred to as a parent device call button). ) 522, a monitor (hereinafter referred to as a parent device monitor) 523, and a general call button 524. Further, the (two) monitor-added master units 503a and 503b are installed in different locations from the place where the monitor-supported master unit 502 is installed in the dwelling unit, and have the same configuration. 530a, 530b, microphones (hereinafter referred to as extension master unit microphones) 531a, 531b, call buttons (hereinafter referred to as extension master unit call buttons) 532a, 532b, monitors (hereinafter referred to as extension master unit monitors). .) 533a, 533b.

  In the intercom apparatus of the conventional example, in order for a visitor at the entrance to the dwelling unit to call a resident in the dwelling unit, the (two) entrance devices with cameras 501a and 501b shown in the system configuration diagram of FIG. Call operation is performed at any of the entrance slave units. Here, when the call button 510a of the entrance slave unit with camera 501a is operated, the monitor master unit 502 connected to the camera entrance slave unit 501a by the two-wire cable L501a. (2 units) additional parent devices with monitors 503a and 503b connected to the parent device speaker 520 and the parent device with monitor 502 by the two-wire cables L502a and L502b (sequentially connected via a crossover wiring) 530a and 530b. The ringing tone is emitted from each of the images, and the visitor's image captured by the camera 511a of the camera-equipped cordless handset 501a (dwelling unit entrance and housing). Entrance including images of near around) the parent machine monitor 523 and (two) with the monitor extension master station 503a monitors with the parent unit 502, 503b of the extension master station monitors 533a, bounded out respectively 533b.

  Further, in order for the resident who confirmed the sounding of the ringing tone and the output of the video to establish a call with the visitor, the monitor-equipped main unit 502 and (two units) shown in the system configuration diagram of FIG. ) A response operation is performed on any of the master units 503a and 503b with a monitor. Here, when the master unit call button 522 of the monitor unit 502 is operated, the monitor unit 502 used by the resident is used. A communication line is formed and formed between the main unit speaker 520 and the main unit microphone 521 and the sub unit microphone 512a and the sub unit speaker 513a of the entrance slave unit with camera 501a used by the visitor via the two-wire cable L501a. A call can be established by transmitting and receiving audio signals via the call line. In particular, a resident can establish a call while confirming a visitor's video.

  Note that there is no prior art document information to be described for the conventional intercom apparatus.

  However, in the conventional intercom apparatus, the (two) entrance slave units with cameras 501a and 501b, the master unit with monitor 502, and the (two) extension master units with monitors 503a and 503b shown in the system configuration diagram of FIG. Need power amplifiers (not shown) for driving the slave speaker 513a, 513b, the master speaker 520, and the extension master speakers 530a, 530b, respectively. Since it was equipped with a class B amplifier driven at a relatively high voltage level of 12V, the power conversion efficiency was low and the power loss due to heat generation increased, and the entrance slave unit with camera, the master unit with monitor, and the extension parent with monitor It was necessary to ensure a high voltage level of the power supply set in each device of the machine. In addition, when the simultaneous call button 524 of the parent device with monitor 502 is operated by a resident, the ringing sounds are simultaneously emitted from the additional parent device speakers 533a and 533b of the (two) additional parent devices with monitor 503a and 503b. Alarm sound as an emergency report such as a fire occurred in the dwelling unit or the like from the master unit speaker 523 of the monitor-equipped master unit 502 and the extension master unit speakers 533a, 533b of the (two) monitor-added master units 503a, 503b In the case of sound emission, there is a problem that the burden of power supply is further increased.

  The present invention has been made to solve the above-described problems, and has high power conversion efficiency as a power amplifier provided in at least one entrance cordless handset, a master phone, and at least one additional master phone, and generates heat. It is an object of the present invention to provide an interphone device that is equipped with a class D amplifier with low power loss and reduces the power supply load, thereby saving power and extending the communication transmission distance.

  In order to achieve the above-described object, an interphone apparatus according to the first aspect of the present invention includes at least one entrance cordless handset connected to a master unit by a two-wire cable or at least one cord by a two-wire cable via the master unit. An extension base unit is connected. The entrance cordless handset has a microphone for transmitting the voice of the visitor to the resident, a speaker for transmitting the voice of the resident to the visitor, a power amplifier for driving the speaker, An interface for transmitting and receiving signals is provided. The main unit and the extension main unit are a microphone for transmitting the resident's voice to the visitor, a speaker for transmitting the visitor's voice to the resident, a power amplifier for driving the speaker, and the resident and the visitor. A howling prevention circuit for switching a call to and from the mobile phone and an interface for transmitting and receiving various signals to and from the entrance unit. The entrance cordless handset, base phone, and extension base phone are equipped with class D amps as power amps.

  The intercom apparatus according to the second aspect of the present invention is configured such that at least one entrance cordless handset is connected to at least one extension cordless handset via a two-wire cable via the master phone or the master phone via a two-wire cable. ing. The entrance cordless handset has a microphone for transmitting the visitor's voice to the resident, a speaker for transmitting the voice from the resident to the visitor, and an interface for sending and receiving various signals to and from the main unit. I have. The master unit and the extension master unit are a microphone for transmitting the resident's voice to the visitor, a speaker for transmitting the visitor's voice to the resident, and for transmitting the resident's voice to the entrance unit. A power amplifier, a power amplifier for driving a speaker, a howling prevention circuit for switching a call between a resident and a visitor, and an interface for transmitting and receiving various signals to and from an entrance cordless handset are provided. The master unit and the extension master unit are equipped with class D amplifiers as power amplifiers.

  According to a third aspect of the present invention, in the intercom apparatus according to the first or second aspect of the present invention, the entrance cordless handset includes a camera for capturing an image of a visitor, and the visitor captured by the camera Has a video modulation circuit with a class D amplifier for transmitting the video signal of the person to the extension master unit via the master unit or the master unit. A monitor for outputting the picked-up video is provided, and a video demodulation circuit for demodulating the video modulation signal modulated through the video modulation circuit of the entrance unit into a video signal is provided.

  According to a fourth aspect of the present invention, in the intercom apparatus according to any one of the first to third aspects of the present invention, the class D amplifier is any one of PWM and ΣΔ modulation methods.

  According to the intercom apparatus of the present invention, at least one entrance child device, parent device, and at least one additional parent device have power for driving the respective child device speakers, parent device speakers, and additional parent device speakers. As an amplifier or as a power amplifier for transmitting audio input to the slave microphone, master microphone, and extension master microphone, among PWM and ΣΔ modulation methods with high power conversion efficiency and low power loss due to heat generation By installing any modulation class D amplifier, the power supply voltage level set in each of the main unit, main unit, and extension main unit can be secured at a low level to save power and communicate The transmission distance can be extended.

  Further, according to the intercom apparatus of the present invention, as the video modulation circuit provided with the camera in at least one entrance cordless handset, any one of PWM and ΣΔ modulation methods with high power conversion efficiency and low power loss due to heat generation It is also possible to mount a class D amplifier of the modulation type.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments to which an interphone device of the invention is applied will be described with reference to the drawings.

  FIG. 1 is a system configuration diagram showing an intercom apparatus according to first and second embodiments of the present invention.

  The intercom apparatus shown in the system configuration diagram of FIG. 1 is at least one entrance cordless handset for capturing a call by a visitor in a dwelling unit calling a resident in the dwelling unit, in this case, capturing an image. / Two camera-equipped cordless handsets 1a and 1b installed at different locations of the dwelling unit entrance with signal processing function, and two-wire cables (hereinafter referred to as parent unit connection cables) L1a and L1b installed in the dwelling unit A call from either one of the two camera-equipped cordless handsets 1a and 1b connected individually is notified together with a video image, and a resident who confirms the call with the visitor In addition to establishing a call, call to at least one extension master unit with a monitor connected by two-wire cables (hereinafter referred to as extension master unit connection cables) L2a and L2b (sequentially connected by crossover wiring). From the main unit with a monitor having a video signal processing / image output function and one of the above-mentioned two entrance units with a camera 1a, 1b. The call is notified with the video output, and the resident who confirms the call establishes a call with the visitor, and simultaneously calls from the monitor-equipped master unit 2 connected by the extension master unit connection cables L2a and L2b At least one extension master unit installed in a different location in the dwelling unit from the installation location of the master unit with monitor 2, and here two extension parents with a monitor having video signal processing / image output functions It consists of the machines 3a and 3b. As shown in the figure, the two extension master units 3a and 3b with a monitor are an extension master unit 3a with a monitor and an extension master unit 3a with a monitor connected to the monitor master unit 2 by an extension master unit connection cable L2a. Is an extension base unit 3b with a monitor connected to the extension base unit connection cable L2b.

  In the system configuration diagram of FIG. 1, the (two) camera-equipped cordless handsets 1a and 1b have the same configuration, and a visitor at the entrance of the dwelling unit operates to call a resident in the dwelling unit. Call buttons 10a and 10b, cameras 11a and 11b for capturing images of the visitor who performed the call operation (including images of the dwelling unit entrance and the vicinity of the dwelling unit entrance), and the voice of the visitor to the resident And 12a, 12b for transmitting the voice of the resident to the visitor (hereinafter referred to as a slave speaker) 13a, 13b. .

  Further, in the system configuration diagram of FIG. 1, the monitor-equipped master unit 2 is described above by the visitor among the (two) entrance slave units with cameras 1a and 1b connected individually by the master unit connection cables L1a and L1b. A speaker (hereinafter referred to as a “main unit speaker”) 20 that emits a ringing sound indicating that there is a call from any of the entrance slave units that have performed the calling operation and transmits the voice of the visitor to the resident. The resident operates (in order to establish a call using the microphone (hereinafter referred to as “main unit microphone”) 21 for transmitting the voice of the resident to the visitor and the parent unit speaker 20 and the parent unit microphone 21 ( Any of the call operations performed by the visitor of the call button 22 (hereinafter referred to as the parent device call button) to be agreed with the response operation, and the (two) camera-equipped slave units 1a and 1b. Taken with the camera of the entrance LCD (Liquid Crystal Display), organic EL (Electro Luminescence), and other monitors (hereinafter referred to as parent device monitors) for displaying the visitor's images (including images of the dwelling unit entrance and the vicinity of the dwelling unit entrance). ) 23 and a simultaneous call button 24 operated by a resident to call the (two) extension main units with monitor 3a, 3b all at once.

  Further, in the system configuration diagram of FIG. 1, the (two) extension master units 3a and 3b with a monitor have the same configuration, and the master unit is connected via the extension master unit connection cables L2a and L2b and the monitor base unit 2. A message indicating that there is a call from any of the (two) camera-equipped cordless handsets 1a and 1b that are individually connected by the connection cables L1a and L1b and for which the above-described calling operation has been performed by the visitor. A speaker (hereinafter referred to as “ringing sound”) or a ringing sound indicating that there is a simultaneous calling in which the general calling button 24 of the monitor-equipped master unit 2 is operated by the resident, and transmitting the voice of the visitor to the resident , Referred to as an extension master unit speaker) 30a, 30b, microphones (hereinafter referred to as extension master unit microphones) 31a, 31b, extension master unit speakers 30a, 30b, and Call buttons (hereinafter referred to as “additional master phone call buttons”) 32a and 32b operated by the resident (to agree with response operation) to establish a call using the base phone microphones 31a and 31b, and (two) Images captured by the camera of any of the entrance cordless devices in which the above-described calling operation has been performed by a visitor of the entrance cordless devices 1a and 1b with cameras (including images of the dwelling unit entrance and the vicinity of the dwelling unit entrance) Monitors such as LCDs and organic ELs (hereinafter referred to as expansion master monitors) 33a and 33b for outputting images.

  FIG. 2A is a block diagram showing a configuration of (two) front door units 1a and 1b with a camera in the intercom apparatus according to the first embodiment of the present invention.

  In the block diagram of FIG. 2 (a), the (two) camera-equipped slave units 1a and 1b have the same configuration, and the above-described call buttons 10a and 10b, cameras 11a and 11b, and slave unit microphones 12a and 12b. , Slave unit speakers 13a and 13b, control circuits for controlling each part of the entrance slave unit (hereinafter referred to as slave unit control circuit) 100a and 100b, and operating power to the constituent parts of the entrance slave unit Power supply circuits (hereinafter referred to as slave device power supply circuits) 101a and 101b and video images of visitors taken by the cameras 11a and 11b (including images of the dwelling unit entrance and the vicinity of the dwelling unit entrance) A signal is modulated into a video modulation signal, for example, a video modulation circuit 102a, 102b for FM modulation, and a power amplifier (hereinafter referred to as a power amplifier) for driving the slave speakers 13a, 13b. 103a, 103b, handset microphones 12a, 12b, handset control circuits 100a, 100b, handset power supply circuits 101a, 101b, video modulation circuits 102a, 102b, handset speaker power amplifier 103a , 103b and an interface (hereinafter referred to as a slave unit I / F) for transmitting and receiving various signals and DC power by forming a signal transmission path / power supply path between the respective base unit connection cables L1a and L1b. ) 104a and 104b.

  FIG. 2B is a block diagram showing the configuration of the monitor base unit 2 in the intercom apparatus according to the first embodiment of the present invention.

  In the block diagram of FIG. 2B, the parent device with monitor 2 includes the above-mentioned parent device speaker 20, parent device microphone 21, parent device call button 22, parent device monitor 23, simultaneous call button 24, and the parent device. A control circuit (hereinafter referred to as a “base unit control circuit”) 200 for controlling each part of the main unit and a DC power source rectified / smoothed with respect to the commercial power source (AC 100V) as an operation power source and FIG. A power supply circuit (hereinafter referred to as a parent circuit) for supplying one of the (two) entrance devices with a camera 1a, 1b shown in the system configuration diagram shown in FIG. Machine power supply circuit) 201, a power amplifier (hereinafter, referred to as a power amplifier for the master speaker) 202 for driving the master speaker 20, and a resident and a visitor who have performed the above-described response operation. Established A howling prevention circuit (hereinafter referred to as a “base unit howling prevention circuit”) 203 for switching the call line of the call to be transmitted and preventing the occurrence of howling due to the feedback of the audio signal from the base unit speaker 20 to the base unit microphone 21. This is a visitor's image (including the image of the dwelling unit entrance and the vicinity of the dwelling unit entrance) captured by the camera of one of the entrance cordless devices where the call operation has been performed by the user, and is modulated via the image modulation circuit. A video demodulating circuit (hereinafter referred to as a master video demodulating circuit) 204 for demodulating, for example, FM demodulating the (FM-modulated) video modulated signal into a video signal, and outputting it to the master monitor 23, and a master Between the control circuit 200, the master unit power supply circuit 201, the master unit howling prevention circuit 203, the master unit video demodulation circuit 204, and the master unit connection cables L1a and L1b, an extension master unit cable Various signals to form respective signal transmission lines / power supply path between the 2a, interface for transmitting and receiving DC power supply (hereinafter, referred to as the master unit I / F.) 205 and are provided.

  FIG. 2C is a block diagram showing a configuration of (two) extension master units 3a and 3b with a monitor in the intercom apparatus according to the first embodiment of the present invention.

  In the block diagram of FIG. 2 (c), the (two) extension master units 3a and 3b with a monitor have the same configuration. The extension master unit speakers 30a and 30b, the extension master unit microphones 31a and 31b, and the extension Base unit call buttons 32a and 32b, expansion base unit monitors 33a and 33b, control circuits (hereinafter referred to as expansion base unit control circuits) 300a and 300b for controlling each component of the expansion base unit, and commercial power ( A DC power source rectified / smoothed with respect to AC 100 V) is used as an operating power source by the visitors among the constituent parts of the extension master unit and the (two) entrance slave units 1a and 1b with a camera shown in the system configuration diagram of FIG. Power supply circuits (hereinafter referred to as extension master unit power supply circuits) 301a and 301b, and extension master unit speakers 30a and 30b. Switch the call line of the call established between the power amplifiers for driving (hereinafter referred to as power amplifiers for extension master speaker) 302a, 302b and the residents and visitors who have performed the above-mentioned response operation, and add them. Howling prevention circuits (hereinafter referred to as additional parent unit howling prevention circuits) 303a and 303b for preventing occurrence of howling due to feedback of audio signals from the parent unit speakers 30a and 30b to the extension parent unit microphones 31a and 31b. This is a visitor's image (including the image of the dwelling unit entrance and the vicinity of the dwelling unit entrance) captured by the camera of one of the entrance cordless devices where the call operation has been performed by the user, and is modulated via the image modulation circuit. Demodulate (FM-modulated) video modulation signal into video signal, for example, FM demodulated and output to extension master monitors 33a and 33b Demodulator circuits (hereinafter referred to as extension master image demodulation circuits) 304a and 304b, extension master unit control circuits 300a and 300b, extension master unit power supply circuits 301a and 301b, extension master unit howling prevention circuits 303a and 303b, extension master units Interfaces for transmitting and receiving various signals and DC power by forming signal transmission paths / power supply paths between the components of the video demodulation circuits 304a and 304b and the extension master unit connection cables L2a and L2b (hereinafter referred to as extension masters). Machine I / F.) 305a and 305b.

  2 (a), 2 (b), and 2 (c), (two) power unit 103a, 103b for the slave unit of the mobile unit 1a and 1b with the camera, and the main unit 2 with the monitor. The power amplifier 202 for the main unit speaker and the power amplifiers 302a and 302b for the additional main unit speakers 3a and 3b of the extension main units 3a and 3b with monitors are respectively class D amplifiers 400 having the configuration shown in the circuit block diagram of FIG. It is equipped with.

  In the circuit block diagram of FIG. 4, the class D amplifier 400 converts a visitor or resident audio signal input to the class D amplifier into PWM (pulse width modulation) and ΣΔ modulation (1 bit quantization modulation) methods. Corresponding to the difference in voltage level between the modulation unit 410 for modulating using any modulation method and the pulse signal of the digital signal format modulated by the modulation unit 410, that is, H (High) / L (Low) In order to prevent the above-described audio signal from being superimposed on the switching frequency generated at the ON / OFF timing of the power switches 411a and 411b and the power switches 411a and 411b such as power MOSFETs that are alternately switched ON / OFF. A high frequency removing circuit 412 for removing a high frequency component of switching and outputting a demodulated analog signal format audio signal; This class D amplifier 400 has the property that the power conversion efficiency is high and the power loss due to heat generation is small compared to the class B amplifier applied in the conventional example.

  The intercom apparatus according to the first embodiment of the present invention configured as described above, that is, the system configuration diagram of FIG. 1 and the block diagrams of FIGS. 2 (a), (b), and (c) (two units) ) In the interphone apparatus composed of the camera-equipped entrance slave units 1a and 1b, the monitor master unit 2, and the (two) monitor extension master units 3a and 3b, specific operations will be described below.

  In order for a visitor at the entrance of the dwelling unit to call a resident who is present in the dwelling unit, any one of the (2) entrance units with cameras 1a and 1b shown in the system configuration diagram of FIG. When the call button 10a of the camera-equipped slave unit 1a is operated here, the slave unit control circuit 100a of the camera-entry slave unit 1a shown in the block diagram of FIG. And a call signal S1 to which call information to that effect is added is output to the slave I / F 104a. This call signal S1 is transmitted from the slave unit I / F 104a to the master unit connection cable L1a and the master unit control circuit 200 via the master unit I / F 205 of the monitor-based master unit 2 shown in the block diagram of FIG. Unit I / F 104a to base unit connection cable L1a, base unit I / F 205 of monitor base unit 2 shown in the block diagram of FIG. 2B, additional base unit connection cable L2a, and block diagram of FIG. From the extension master unit I / F 305a of the monitor extension base unit 3a, the extension master unit control circuit 300a and the above extension master unit I / F 305a to the extension master unit connection cable L2b and the extension master unit I of the monitor extension base unit 3b / F 305b to be transmitted to the extension master unit control circuit 300b.

  In the block diagram of FIG. 2 (b), the base unit control circuit 200 of the base unit with monitor 2 detects that there is a call from the entrance unit with camera 1a based on the input call signal S1, and to that effect. Is emitted from the main unit speaker 20, and the main unit monitor 23 and the main unit video demodulation circuit 204 are respectively driven and controlled, and the main unit power supply circuit 201 is controlled. The operating power from the main unit power supply circuit is supplied to the sub unit via the main unit I / F 205, the main unit connection cable L1a, and the sub unit I / F 104a of the main unit with camera 1a shown in the block diagram of FIG. By supplying operation power to the circuit 101a as a call (calling / calling) state, the power supply from the slave unit power supply circuit 101a becomes the operation power source and is controlled by the camera 11a controlled by the slave unit control circuit 100a. Imaging outgoing manipulate visitor of images performed (including the image of the surrounding vicinity of the dwelling unit entrance and dwelling entrance) is started.

  In the block diagram of FIG. 2 (c), the extension master unit control circuits 300a, 300b of the (two) extension master units with monitor 3a, 3b are respectively connected to the entrance slave unit with camera 1a based on the input call signal S1. Is detected and the ringing sound for notifying the resident is emitted from the extension master unit speakers 30a, 30b, and the extension master unit monitors 33a, 33b, the extension master unit video demodulation circuit Drive control of 304a and 304b is performed.

  Also, in the block diagram of FIG. 2A, the video signal S2 of the visitor's video (including the video of the dwelling unit entrance and the vicinity of the dwelling unit entrance) captured by the camera 11a of the camera-equipped cordless handset 1a is: As the video modulation signal S2a modulated by the video modulation circuit 102a (FM modulation), the slave unit I / F 104a to the master unit connection cable L1a, the master unit I / F of the monitor base unit 2 shown in the block diagram of FIG. Via the F205, the parent device video demodulation circuit 204, the child device I / F 104a to the parent device connection cable L1a, the parent device I / F 205 of the parent device with monitor 2 shown in the block diagram of FIG. The extension master unit is connected from the extension master unit video demodulation circuit 304a and the above extension master unit I / F 305a via the extension master unit I / F 305a of the monitor extension master unit 3a shown in the block diagram of FIG. K Le L2b, respectively to the extension master station video demodulation circuit 304b through the extension master station I / F305b dated monitor extension master station 3b is transmitted.

  Further, in the block diagram of FIG. 2B, the master video demodulation circuit 204 of the monitor-equipped master unit 2 demodulates (FM-demodulates) the input video modulation signal S2a into the video signal S2, and the master monitor 23 By outputting to the main unit monitor 23, it is possible to display the video of the visitor who performed a call operation on the camera-equipped entrance slave unit 1a (including the dwelling unit entrance and the image in the vicinity of the dwelling unit entrance).

  Further, in the block diagram of FIG. 2C, the master video demodulation circuits 304a and 304b of the (two) extension master units 3a and 3b with a monitor convert the input video modulation signal S2a into the video signal S2. By demodulating (FM demodulating) and outputting to the extension master monitors 33a and 33b, images of visitors who performed a call operation on the camera-equipped slave unit 1a (including images of the dwelling unit entrance and the vicinity of the dwelling unit entrance) ) Can be displayed on the extension master monitors 33a and 33b.

  Next, the ringing sound is emitted from the base unit speaker 20 of the base unit 2 with the monitor shown in the system configuration diagram of FIG. 1 and the block diagram of FIG. 1 is a system configuration diagram and the block diagram of FIG. 2 (c) shows the ringing sound from the extension master unit speakers 30a and 30b of the (two) extension master units 3a and 3b with monitor, and the extension master unit monitor 33a. , 33b, a resident who has confirmed the above-mentioned call notification made by any of the parent devices (additional parent device), here, the above-mentioned call made by the monitor-equipped parent device 2 When the resident who confirmed the notification operates the base unit call button 22 as a response operation, the base unit control circuit 200 shown in the block diagram of FIG. Machine feedback prevention circuit 203 With controlled, the response signal S3 obtained by adding the response information to that effect is output to the master unit I / F 205. This response signal S3 is transmitted from the master unit I / F 205 to the slave unit control circuit 100a via the master unit connection cable L1a and the slave unit I / F 104a of the entrance slave unit with camera shown in the block diagram of FIG. Is done.

  In the block diagram of FIG. 2 (a), the slave unit control circuit 100a of the entrance slave unit with camera 1a has been operated by the resident on the monitor master unit 2 based on the input response signal S3. Is detected and the power amplifier 103a for the handset speaker is driven and controlled, so that the handset microphone 12a and handset speaker 13a of the entrance handset with camera 1a used by the visitor, the power amplifier 103a for the handset speaker, and the handset Residential via the I / F 104a, the master unit connection cable L1a, the master unit I / F 205 of the master unit with monitor 2 shown in the block diagram of FIG. 2B, the master unit howling prevention circuit 203, and the master unit speaker power amplifier 202 A call line between the parent speaker 20 and the parent microphone 21 used by the person is formed.

  In the call state in which the above-described call line is formed, the slave unit control circuit 100a of the entrance slave unit with camera 1a shown in the block diagram of FIG. 2A and the parent with monitor shown in the block diagram of FIG. The base unit control circuit 200 of the machine 2 holds the drive control to the camera 11a and the video modulation circuit 102a and the drive control to the base unit monitor 23 and the base unit video demodulation circuit 204, respectively, until this call is finished. During this time, the visitor's video (including the video of the dwelling unit entrance and the vicinity of the dwelling unit entrance) captured by the camera 11a can be displayed on the master unit monitor 23. On the other hand, the extension master unit control circuits 300a and 300b of the (two) extension master units 3a and 3b with a monitor shown in the block diagram of FIG. 4A have passed a predetermined time since the call signal S1 was detected. Later, by stopping the drive control to the extension master monitors 33a and 33b and the extension master video demodulation circuits 304a and 304b, the camera of the entrance slave unit with a camera 1a in the call state in which the above-described call line is formed. The visitor images (including images of the dwelling unit entrance and the vicinity of the dwelling unit entrance) captured at 11a are not displayed on the extension master monitors 33a and 33b.

  Next, in the call state in which the above-described call line is formed, the resident's voice signal S10 input to the base unit microphone 21 of the base unit with monitor 2 shown in the block diagram of FIG. To the power amplifier 103a for the slave unit speaker via the howl prevention circuit 203, the master unit I / F 205, the master unit connection cable L1a, and the slave unit I / F 104a of the entrance slave unit with camera shown in the block diagram of FIG. The signal is transmitted to the modulation unit 410 of the class D amplifier 400 shown in the circuit block diagram of FIG.

  In the circuit block diagram of FIG. 4, the modulation unit 410 of the D-class amplifier 400 mounted on the slave speaker power amplifier 103a of the camera-equipped slave unit 1a shown in the block diagram of FIG. A pulse signal S10a in the form of a digital signal obtained by modulating the signal S10 using any one of the PWM and ΣΔ modulation methods is output. The power switches 411a and 411b are alternately switched on / off at the H / L timing of the pulse signal S10a, and the power supply time from the slave unit power supply circuit 101a to the slave unit speaker 13a is controlled based on the pulse width. To do. Further, the high frequency removal circuit 412 removes the high frequency component and demodulates it in an analog signal format in order to prevent the high frequency component generated by the switching of the power switches 411a and 411b from being superimposed on the audio signal S10. By generating the audio signal S10b and outputting it to the child device speaker 13a, the voice of the resident who has made a response operation on the monitor-equipped parent device 2 is emitted from the child device speaker 13a as a received sound.

  On the other hand, in the call state in which the above-described call line is formed, the visitor's voice signal S20 input to the child microphone 12a of the camera-equipped child child device 1a shown in the block diagram of FIG. Installed in I / F 104a to main unit connection cable L1a, main unit I / F 205 of main unit with monitor 2 shown in the block diagram of FIG. 2B, and main unit speaker power amplifier 202 via main unit howling prevention circuit 203 4 is transmitted to the modulation unit 410 of the class D amplifier 400 shown in the circuit block diagram of FIG.

  In the circuit block diagram of FIG. 4, the modulation unit 410 of the class D amplifier 400 mounted on the master speaker power amplifier 202 of the master unit 2 with monitor shown in the block diagram of FIG. For S20, a pulse signal S20a in the form of a digital signal modulated using any one of PWM and ΣΔ modulation methods is output. The power switches 411a and 411b are alternately switched on / off at the H / L timing of the pulse signal S20a, and control the power supply time from the parent power supply circuit 201 to the parent speaker 20 based on the pulse width. To do. Further, the high frequency removal circuit 412 removes the high frequency component and demodulates it in an analog signal format in order to prevent the high frequency component generated by the switching of the power switches 411a and 411b from being superimposed on the audio signal S20. By generating the audio signal S20b and outputting it to the main unit speaker 20, the voice of the visitor who has performed the calling operation on the camera-equipped cordless handset 1a is emitted from the main unit speaker 20 as a received sound, For the resident, the call can be established while checking the video of the visitor.

  In the block diagram of FIG. 2B, the master unit howling prevention circuit 203 of the master unit with monitor 2 transmits the audio signal S10 from the master unit microphone 21 to the master unit I / F 205. By blocking the signal transmission path from the machine I / F 205 to the power amplifier 202 for the master speaker, the voice of the visitor emitted from the master speaker 20 is returned to the master microphone 21, that is, howling occurs. Can be prevented and good call quality can be secured.

  As described above, according to the intercom apparatus according to the first embodiment of the present invention, the (two) entrance devices with a camera 1a shown in the block diagrams of FIGS. 2 (a), 2 (b), and 2 (c). 1b, power amplifiers 103a, 103b for the slave unit speakers, a power amplifier 202 for the master unit speaker of the master unit 2 with monitor, a power amplifier 302a for the extension master unit speakers of the (two) extension master units 3a, 3b with monitor 302b is installed with the class D amplifier 400 having the configuration shown in the circuit block diagram of FIG. 4 having high power conversion efficiency and low power loss due to heat generation. The voltage level of the power supply set in each device of the extension master can be secured at a low level, and power saving and communication transmission distance can be extended.

  Further, another embodiment having the same effect as that of the first embodiment described above will be described below as an intercom apparatus according to the second embodiment of the present invention.

  Further, in the intercom apparatus according to the second embodiment of the present invention, the same components as those of the above-described intercom apparatus of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 3A is a block diagram showing a configuration of (two) front door units 1a and 1b with a camera in the intercom apparatus according to the second embodiment of the present invention.

  In the block diagram of FIG. 3A, (two) camera-equipped slave units 1a and 1b have the same configuration, and the above-described call buttons 10a and 10b, cameras 11a and 11b, and slave unit microphones 12a and 12b. , Handset speaker 13a, 13b, handset control circuit 100a, 100b, handset power supply circuit 101a, 101b, video modulation circuit 102a, 102b, handset microphone 12a, 12b, handset speaker 13a, 13b, handset control circuit 100a and 100b, slave unit power supply circuits 101a and 101b, video modulation circuits 102a and 102b, and signal transmission paths / power supply paths between the master unit connection cables L1a and L1b are formed, respectively. Slave unit I / Fs 105a and 105b for transmission and reception are provided.

  FIG. 3B is a block diagram showing the configuration of the monitor base unit 2 in the intercom apparatus according to the second embodiment of the present invention.

  In the block diagram of FIG. 3B, the parent device with monitor 2 includes the parent device speaker 20, the parent device microphone 21, the parent device call button 22, the parent device monitor 23, the simultaneous call button 24, and the parent device control circuit. 200, parent device power supply circuit 201, parent device speaker power amplifier 202, parent device howling prevention circuit 203, parent device video demodulation circuit 204, and a resident's voice input to parent device microphone 21 are amplified and visited. , A power amplifier 206 (hereinafter referred to as a “base amplifier power amplifier”), a master control circuit 200, a master power supply circuit 201, and a master. Unit howling prevention circuit 203, base unit video demodulation circuit 204, power unit 206 for base unit microphone, signal transmission path between base unit connection cables L1a and L1b, and extension base unit cable L2a Various signals the power supply path formed respectively, and the master unit I / F 207 for transmitting and receiving the DC power source is provided.

  FIG. 3C is a block diagram showing a configuration of (two) extension base units 3a and 3b with a monitor in the intercom apparatus according to the second embodiment of the present invention.

  In the block diagram of FIG. 3C, the (two) extension master units 3a and 3b with a monitor have the same configuration, and the extension master unit speakers 30a and 30b, the extension master unit microphones 31a and 31b, and the extension unit described above. Master phone call buttons 32a, 32b, extension master monitor 33a, 33b, extension master control circuit 300a, 300b, extension master power supply circuit 301a, 301b, extension master speaker power amplifiers 302a, 302b, prevention of extension master howling Any of the above-described call operations performed by a visitor by amplifying the resident's voice input to the circuits 303a and 303b, the extension master unit video demodulation circuits 304a and 304b, and the extension master unit microphones 31a and 31b Power amplifiers (hereinafter referred to as extension master microphone power amplifiers) 306a and 306b for transmission to the entrance slave unit, and an extension master unit control circuit 00a, 300b, extension master unit power supply circuits 301a, 301b, extension master unit howling prevention circuits 303a, 303b, extension master unit video demodulation circuits 304a, 304b, configuration units of extension master unit microphone power amplifiers 306a, 306b, and extension master unit Additional base unit I / Fs 307a and 307b are provided for transmitting and receiving various signals and DC power by forming a signal transmission path / power supply path between the connection cables L2a and L2b, respectively.

  3 (b) and 3 (c), the master speaker power amplifier 202 and the master microphone power amplifier 206 of the monitor-equipped master unit 2, and the (two) monitor extension master units 3a. 3b, the power amplifiers 302a and 302b for additional master unit speakers and the power amplifiers 306a and 306b for additional base unit microphones are each equipped with a class D amplifier 400 having the configuration shown in the circuit block diagram of FIG.

  The intercom apparatus according to the second embodiment of the present invention thus configured, that is, the system configuration diagram of FIG. 1 and the block diagrams of FIGS. 3A, 3B, and 3C (two units) ) In the interphone apparatus composed of the camera-equipped entrance slave units 1a and 1b, the monitor master unit 2, and the (two) monitor extension master units 3a and 3b, specific operations will be described below.

  In the intercom apparatus according to the second embodiment of the present invention, in order for a visitor at the entrance to the dwelling unit to call a resident in the dwelling unit, the (two) cameras shown in the system configuration diagram of FIG. By operating the call button 10a of the camera-equipped entrance cordless handset 1a out of the attached entrance cordless handsets 1a and 1b, the ringing sound is emitted from the master phone speaker 20 of the monitor-attached master phone 2 and the visitor video is displayed on the master phone monitor 23. (Including the entrance to the dwelling unit and the vicinity of the dwelling unit entrance), and the ringing sound is emitted from the (2) extension main unit speakers 3a and 3b with the extension main unit speakers 30a and 30b. Since the operations until the extension master monitors 33a and 33b display the visitor's video (including the video of the dwelling unit entrance and the vicinity of the dwelling unit entrance) are the same as those in the first embodiment, the explanation will be given. Omitted.

  Next, the ringing sound is emitted from the main unit speaker 20 of the main unit 2 with the monitor shown in the system configuration diagram of FIG. 1 and the block diagram of FIG. 1 is a system configuration diagram and a block diagram of FIG. 3 (c) shows the ringing sound from the extension master unit speakers 30a and 30b of the (two) extension master units 3a and 3b with monitor, and the extension master unit monitor 33a. , 33b, a resident who has confirmed the above-mentioned call notification made by any of the parent devices (additional parent device), here, the above-mentioned call made by the monitor-equipped parent device 2 When the resident who has confirmed the notification operates the base unit call button 22 as a response operation, the base unit control circuit 200 shown in the block diagram of FIG. Machine howling prevention circuit 203, parent machine microphone With the power amplifier 206 is driven and controlled respectively, the response signal S4 obtained by adding the response information to that effect is output to the master unit I / F 207. This response signal S4 is transmitted from the master unit I / F 207 to the slave unit control circuit 100a via the master unit connection cable L1a and the slave unit I / F 105a of the entrance slave unit with camera shown in the block diagram of FIG. Is done.

  In the block diagram of FIG. 3 (a), the slave unit control circuit 100a of the entrance slave unit with camera 1a has been operated by the resident in the monitor base unit 2 based on the input response signal S4. Is detected. At this time, the handset microphone 12a and handset speaker 13a of the entrance slave unit with camera 1a used by the visitor, the slave unit I / F 105a, the base unit connection cable L1a, and the master with monitor shown in the block diagram of FIG. Between the parent device speaker 20 and the parent device microphone 21 used by a resident through the parent device I / F 207, the parent device microphone power amplifier 206, the parent device howling prevention circuit 203, and the parent device speaker power amplifier 202. The call line is formed.

  In the call state in which the above-described call line is formed, the slave unit control circuit 100a of the entrance slave unit with a camera shown in the block diagram of FIG. 3A and the parent with a monitor shown in the block diagram of FIG. The base unit control circuit 200 of the machine 2 holds the drive control to the camera 11a and the video modulation circuit 102a and the drive control to the base unit monitor 23 and the base unit video demodulation circuit 204, respectively, until this call is finished. During this time, the visitor's video (including the video of the dwelling unit entrance and the vicinity of the dwelling unit entrance) captured by the camera 11a can be displayed on the master unit monitor 23. On the other hand, the extension master unit control circuits 300a and 300b of the (two) extension master units 3a and 3b with a monitor shown in the block diagram of FIG. 3C have passed a predetermined time since the call signal S1 was detected. Later, by stopping the drive control to the extension master monitors 33a and 33b and the extension master video demodulation circuits 304a and 304b, the camera of the entrance slave unit with a camera 1a in the call state in which the above-described call line is formed. The visitor images (including images of the dwelling unit entrance and the vicinity of the dwelling unit entrance) captured at 11a are not displayed on the extension master monitors 33a and 33b.

  Next, in the call state in which the above-described call line is formed, the resident's voice signal S30 input to the base unit microphone 21 of the base unit with monitor 2 shown in the block diagram of FIG. The signal is transmitted via the howling prevention circuit 203 to the modulation section 410 of the class D amplifier 400 shown in the circuit block diagram of FIG.

  In the circuit block diagram of FIG. 4, the modulation unit 410 of the class D amplifier 400 mounted on the master microphone power amplifier 206 of the master unit 2 with monitor shown in the block diagram of FIG. For S30, a pulse signal S30a in the form of a digital signal modulated using any one of the PWM and ΣΔ modulation methods is output. The power switches 411a and 411b are alternately switched on / off at the H / L timing of the pulse signal S30a, and the high frequency removal circuit 412 has high frequency components generated by the switching of the power switches 411a and 411b as described above. In order to prevent the signal from being superimposed on the signal S30, an audio signal S30b in an analog signal format is generated by removing the high frequency component and demodulating. The audio signal S30b is transmitted from the master unit I / F 207 to the slave unit speaker 13a via the master unit connection cable L1a and the slave unit I / F 105a of the entrance slave unit with a camera shown in the block diagram of FIG. As a result, the voice of the resident who performed the response operation on the monitor-attached master unit 2 is emitted from the slave unit speaker 13a as the received sound.

  On the other hand, in a call state in which the above-described call line is formed, a visitor's voice signal S40 input to the handset microphone 12a of the camera-equipped handset 1a shown in the block diagram of FIG. Installed in the power amplifier 202 for the main unit speaker through the main unit connection cable L1a from the I / F 105a, the main unit I / F 207 of the main unit with monitor 2 shown in the block diagram of FIG. 3B, and the main unit howling prevention circuit 203 4 is transmitted to the modulation unit 410 of the class D amplifier 400 shown in the circuit block diagram of FIG.

  In the circuit block diagram of FIG. 4, the modulation unit 410 of the class D amplifier 400 mounted on the master speaker power amplifier 202 of the master unit 2 with monitor shown in the block diagram of FIG. In S40, a pulse signal S40a in the form of a digital signal modulated using any one of the PWM and ΣΔ modulation methods is output. The power switches 411a and 411b are alternately switched on / off at the H / L timing of the pulse signal S40a, and the power supply time from the parent device power supply circuit 201 to the parent device speaker 20 is controlled based on the pulse width. To do. Further, the high-frequency removal circuit 412 removes the high-frequency component and demodulates it in an analog signal format in order to prevent the high-frequency component generated by the switching of the power switches 411a and 411b from being superimposed on the audio signal S40. By generating the audio signal S40b and outputting it to the main unit speaker 20, the voice of the visitor who has performed a call operation on the camera-equipped cordless handset 1a is emitted from the main unit speaker 20 as a received sound, For the resident, the call can be established while checking the video of the visitor.

  In the block diagram of FIG. 3B, the master unit howling prevention circuit 203 of the monitor master unit 2 receives the audio signal S30 from the master unit microphone 21 via the master unit microphone power amplifier 206. In the case of transmission to F207, the signal transmission path from the master unit I / F 207 to the master speaker power amplifier 202 is cut off, whereby the master unit microphone of the visitor's voice emitted from the master speaker 20 Returning to 21, that is, howling is prevented and good call sound quality can be secured.

  As described above, according to the intercom apparatus according to the second embodiment of the present invention, the master speaker power amplifier 202 and the master of the master unit 2 with the monitor shown in the block diagrams of FIGS. The power amplifier 206 for the microphone, the power amplifiers 302a and 302b for the extension master speakers of the extension master units 3a and 3b with two monitors, and the power amplifiers 306a and 306b for the extension master microphones have high power conversion efficiency and heat. By mounting the class D amplifier 400 having the configuration shown in the circuit block diagram of FIG. 4 where power loss due to generation of power is small, the power supply voltage set in each device of the monitor-equipped master unit and monitor-added master unit The level can be secured at a low level, and power saving and communication transmission distance can be extended.

  In each of the first and second embodiments of the present invention, the (two) entrance devices with cameras 1a and 1b shown in the block diagrams of FIGS. 2 (a) and 3 (a) are provided. As the video modulation circuits 102a and 102b, the class D amplifier 400 having the configuration shown in the circuit block diagram of FIG. 4 having high power conversion efficiency and low power loss due to heat generation, similar to the above-mentioned power amplifiers 103a and 103b for the slave speaker. The video modulation circuit equipped with is also suitable, and by applying this video modulation circuit, the voltage level of the power supply set in the entrance unit with the camera can be secured at a low level, and power saving can be achieved. .

  Further, in each of the first and second embodiments of the present invention, at least one entrance cordless handset has a video imaging / signal processing function, that is, has cameras 11a and 11b and video modulation circuits 102a and 102b. Applying two entrance slave units 1a and 1b with a camera, the master unit and at least one extension master unit also have video signal processing / image output functions, that is, the master unit video demodulation circuit 204 and the extension master unit The monitor base unit 2 having the video demodulation circuits 304a and 304b, the base unit monitor 23 and the extension base unit monitors 33a and 33b and the two monitor extension base units 3a and 3b are applied. Applicable to the main unit and extension master unit with the above-mentioned video signal processing / output function inadequate as the main unit, master unit, and extension master unit with inadequate imaging / signal processing functions Even if the same effects as described above.

FIG. 1 is a system configuration diagram showing an intercom apparatus according to first and second embodiments of the present invention. FIGS. 2A, 2B, and 2C are blocks respectively showing configurations of an entrance slave unit with a camera, a master unit with a monitor, and an extension master unit with a monitor in the intercom apparatus according to the first embodiment of the present invention. FIG. FIGS. 3A, 3B, and 3C are blocks respectively showing configurations of an entrance slave unit with a camera, a master unit with a monitor, and an extension master unit with a monitor in an intercom apparatus according to a second embodiment of the present invention. FIG. FIG. 4 shows a D-class amplifier mounted on a power amplifier of each device of an entrance slave unit with a camera, a master unit with a monitor, and an extension master unit with a monitor in the intercom apparatus according to the first and second embodiments of the present invention. It is a circuit block diagram which shows the structure. FIG. 5 is a system configuration diagram showing a conventional intercom apparatus.

Explanation of symbols

1a, 1b ...... Entrance unit with camera (entrance unit)
11a, 11b …… Camera 12a, 12b …… Slave unit microphone (microphone)
13a, 13b ...... Slave unit speakers (speakers)
102a, 102b ... Video modulation circuit 103a, 103b ... Power amplifier (power amplifier) for handset speaker
104a, 104b, 105a, 105b ... Slave unit I / F (interface)
2 ... Base unit with monitor 20 ... Base unit speaker (speaker)
21 …… Base microphone (microphone)
23 …… Master monitor (monitor)
202 …… Power amplifier for main unit speaker (power amplifier)
203 …… Master unit howling prevention circuit (howling prevention circuit)
204 …… Master image demodulation circuit (image demodulation circuit)
205, 207 ... Master unit I / F (interface)
206 …… Power amplifier for main unit microphone
3a, 3b: Additional base unit with monitor 30a, 30b: Additional base unit speakers (speakers)
31a, 31b ... Extension base unit microphone (microphone)
33a, 33b: Additional master monitor (monitor)
302a, 302b ...... Power amplifier for extension main unit speaker (power amplifier)
303a, 303b ...... Extension parent unit howling prevention circuit (howling prevention circuit)
304a, 304b ... Additional master image demodulation circuit (image demodulation circuit)
305a, 305b, 307a, 307b ... Additional master unit I / F (interface)
306a, 306b …… Power amplifier for extension base unit microphone (power amplifier)
L1a, L1b ... Master unit connection cable (2-wire cable)
L2a, L2b ... Extension base unit connection cable (2-wire cable)

Claims (4)

At least one entrance cordless handset (1a, 1b) is connected to the master unit (2) by a two-wire cable (L1a, L1b) or at least one extension parent by a two-wire cable (L2a, L2b) via the master unit. Connect machine (3a, 3b)
The entrance cordless handset includes a microphone (12a, 12b) for transmitting a voice of a visitor to a resident, a speaker (13a, 13b) for transmitting a voice from the resident to the visitor, and the speaker. Power amplifiers (103a, 103b) for driving, and interfaces (104a, 104b) for transmitting / receiving various signals to / from the master unit,
The master unit and the extension master unit include a microphone (21, 31a, 31b) for transmitting the voice of the resident to the visitor, and a speaker (20 for transmitting the voice of the visitor to the resident). 30a, 30b), a power amplifier (202, 302a, 302b) for driving the speaker, a howling prevention circuit (203, 303a, 303b) for switching a call between the resident and the visitor, Provided with interfaces (205, 305a, 305b) for transmitting and receiving various signals to and from the entrance cordless handset,
A class D amplifier is mounted as the power amplifier in the entrance slave unit, the master unit, and the extension master unit. At least one entrance cordless handset (1a, 1b) is connected to the master unit (2) by a two-wire cable (L1a, L1b) or at least one extension parent by a two-wire cable (L2a, L2b) via the master unit. Connect machine (3a, 3b)
The entrance cordless handset includes a microphone (12a, 12b) for transmitting the voice of the visitor to a resident, a speaker (13a, 13b) for transmitting the voice from the resident to the visitor, the parent Interface (106a, 106b) for sending and receiving various signals to and from the machine,
The master unit and the extension master unit include a microphone (21, 31a, 31b) for transmitting the voice of the resident to the visitor, and a speaker (20 for transmitting the voice of the visitor to the resident). 30a, 30b), a power amplifier (206, 306a, 306b) for transmitting the resident's voice to the entrance cordless handset, a power amplifier (202, 302a, 302b) for driving the speaker, A howling prevention circuit (203, 303a, 303b) for switching a call between a resident and the visitor, and an interface (207, 307a, 307b) for transmitting / receiving various signals to / from the entrance cordless handset Prepared,
A class D amplifier is mounted as the power amplifier in each of the master unit and the extension master unit.   The entrance cordless handset includes a camera (11a, 11b) for picking up an image of a visitor, and the video signal of the visitor picked up by the camera is added to the extension via the parent device or the parent device. A video modulation circuit (102a, 102b) equipped with a class D amplifier for transmission to the master unit is provided, and the master unit and the extension master unit output images captured by the camera of the entrance slave unit. Monitor (23, 33a, 33b), and a video demodulation circuit (204, 304a, 304b) for demodulating the video modulation signal modulated via the video modulation circuit of the entrance unit into a video signal The intercom apparatus according to claim 1 or 2, characterized by the above-mentioned.   The interphone apparatus according to any one of claims 1 to 3, wherein the class D amplifier is one of a PWM modulation method and a ΣΔ modulation method.

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