JP7122587B2 - Lobby station, door phone system and communication method - Google Patents

Description

The present disclosure relates to a lobby station, door phone system and communication method.

2. Description of the Related Art A door phone system for a detached house consisting of an entrance handset installed at the entrance outside the house and a base station inside the house is widely used. Generally, in a door phone system, a door slave unit and a master unit are connected by a two-wire cable.

2. Description of the Related Art Due to the recent heightened awareness of crime prevention, etc., there is a strong demand for higher image quality of images. For this reason, in door phone systems for detached houses, studies are underway to switch from the analog system to the digital system for communication via the two-wire cable. A digital intercom system can transmit and receive a large amount of data, so that users can view high-definition video. Also, a door phone system has been developed in which an existing two-wire cable can be used as it is for low cost and easy installation when switching to a digital system.

In recent years, door phone systems for collective housing such as condominiums have become popular. In a door phone system for collective housing as well, it is common that each device is connected by a two-wire cable.

In the case of an analog door phone for collective housing, deterioration in image quality of video becomes noticeable due to signal deterioration caused by passing through a plurality of distribution devices (repeaters) and signal deterioration caused by an increase in wiring length. Therefore, in the future, door intercom systems for housing complexes are expected to switch from analog systems to digital systems in order to meet the demand for higher image quality.

In Patent Document 1, a collective entrance device (lobby station) installed at the common entrance of a collective housing and a living room main unit installed in each dwelling unit for residents to respond to calls from the collective entrance device an indoor monitor), and a controller (distribution device) connected to the entrance door unit via the two-wire cable of the common area and to the master unit of each dwelling unit via the two-wire cable of each dwelling unit. A digital multi-housing intercom system (a multi-housing intercom system) is disclosed.

In door phone systems for multi-family dwellings as well, it is desirable to use existing equipment (two-wire cables, devices, etc.) as much as possible when switching from the analog system to the digital system for low cost and easy installation. . The door phone system for collective housing described in Patent Document 1 can use an existing two-wire cable as it is.

Japanese Patent Application Laid-Open No. 2007-202047

However, in conventional digital multi-family door phone systems, when switching from the analog system, it is necessary to replace all the devices (lobby station, room monitor, distribution device) or add new devices. .

For example, in the door phone system for collective housing of Patent Document 1, it is necessary to newly add a digital signal transmission adapter and a combiner in order to realize digital communication.

The present disclosure is a lobby station and a door phone that can use many of the existing facilities (two-wire cable, distribution device, etc.) as they are without adding a new device when switching from an analog system to a digital system. It is to provide a system and communication method.

A lobby station of the present disclosure includes a lobby station, an indoor monitor, and a distribution device that relays communication between the lobby station and the indoor monitor, and the lobby station transmits the The lobby station of an intercom system for transmitting a video signal and a downstream audio signal to an indoor monitor, and the indoor monitor transmitting an upstream audio signal to the lobby station via the distribution device, wherein a subject is photographed and digitalized. A camera module that generates video data and performs compression processing on the video data, a control unit that converts the compressed digital video data into packets, and digital modulation on the digital data string of the packets. and a digital modulation unit for outputting the video signal of a carrier wave within a preset frequency band.

A door phone system of the present disclosure includes a lobby station, an indoor monitor, and a distribution device that relays communication between the lobby station and the indoor monitor, wherein the lobby station photographs a subject. to generate digital video data, perform compression processing on the video data, convert the compressed digital video data into packets, and digitally modulate the digital data string of the packets in advance. generating a video signal of a carrier wave within a set frequency band, transmitting the video signal and the downstream audio signal to the indoor monitor via the distribution device, and transmitting the video signal and the downstream audio signal to the indoor monitor via the distribution device; Send upstream audio signals to the station.

A communication method of the present disclosure is a communication method for a door phone system having a lobby station, an indoor monitor, and a distribution device that relays communication between the lobby station and the indoor monitor, wherein the lobby station: A subject is photographed to generate digital video data, compression processing is performed on the video data, the compressed digital video data is converted into packets, and digital modulation is performed on the digital data string of the packets. to generate a video signal of a carrier wave within a preset frequency band, transmit the video signal and the downstream audio signal to the indoor monitor via the distribution device, and the indoor monitor transmits the video signal via the distribution device. to transmit an upstream voice signal to the lobby station.

It should be noted that these generic or specific aspects may be implemented in systems, integrated circuits, computer programs, or recording media, and any combination of systems, devices, methods, integrated circuits, computer programs and recording media. may be implemented with

According to one aspect of the present disclosure, much of the existing equipment can be used as-is without adding new equipment when switching from analog to digital.

System configuration diagram showing configuration of door phone system according to Embodiment 1 of the present disclosure A diagram showing a frame format and a time slot format according to Embodiment 1 of the present disclosure Block diagram showing configuration of lobby station according to Embodiment 1 of the present disclosure A diagram showing an example of a button layout of a lobby station according to Embodiment 1 of the present disclosure Block diagram showing the configuration of an indoor monitor according to Embodiment 1 of the present disclosure Block diagram showing the configuration of a distribution device according to Embodiment 1 of the present disclosure FIG. 4 is a diagram for explaining the time difference between the specified number of frames due to the difference in crystal oscillation frequency according to the first embodiment of the present disclosure; Block diagram showing the internal configuration of the crystal oscillation frequency control unit of the lobby station according to the first embodiment of the present disclosure FIG. 2 is a block diagram showing the internal configuration of the crystal oscillation unit of the lobby station according to the first embodiment of the present disclosure; Flow chart showing the flow of relay control of the distribution device according to Embodiment 1 of the present disclosure FIG. 3 is a sequence diagram from the standby state to the communication state of the door phone system according to Embodiment 1 of the present disclosure (lobby station activation). FIG. 3 is a sequence diagram from the standby state to the communication state of the door phone system according to Embodiment 1 of the present disclosure (indoor monitor activation) Diagram explaining the frequency band of each signal transmitted and received by the analog lobby station FIG. 5 is a diagram for explaining frequency bands of signals transmitted and received by the lobby station according to Embodiment 1 of the present disclosure; Block diagram showing configuration of lobby station according to Embodiment 2 of the present disclosure Block diagram showing the configuration of an indoor monitor according to Embodiment 2 of the present disclosure

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of substantially the same configurations may be omitted. This is to avoid unnecessary verbosity in the following description and to facilitate understanding by those skilled in the art.

It should be noted that the accompanying drawings and the following description are provided for a thorough understanding of the present disclosure by those skilled in the art and are not intended to limit the claimed subject matter.

(Embodiment 1)
<Overview of the system>
First, the outline of the intercom system of the present disclosure will be described with reference to FIG. As shown in FIG. 1, the door phone system 1 comprises a lobby station 100, an indoor monitor 200, and a distribution device 300. FIG. The lobby station 100 is a device used by a visitor of an apartment complex to call a resident of the destination, and is installed, for example, at a common entrance (lobby) on the ground floor of an apartment building. The indoor monitor 200 is a device for a resident to respond to a call from a visitor, and is installed in each room (or each dwelling unit). The distribution device 300 is a device that relays between the lobby station 100 and the indoor monitor 200, and is installed on each floor of a building, for example.

Lobby station 100 is connected to one distribution device 300-1 via a two-wire cable.

The distribution devices 300 are connected together in a daisy-chain wiring via two-wire cables. Specifically, the distribution device 300-1 is connected to the preceding lobby station 100 and the subsequent distribution device 300-2. Other distribution devices 300-i (where i is an integer equal to or greater than 2) are connected to the front-stage distribution device 300-i-1 and the rear-stage distribution device 300-i+1. Also, each distribution device 300 is connected to each of the plurality of indoor monitors 200 by star wiring via a two-wire cable.

Lobby station 100 transmits a video signal and an audio signal to indoor monitor 200 of the communication partner. Each room monitor 200 transmits audio signals to the lobby station 100 . Each indoor monitor 200 also controls the camera of the lobby station 100 . Distribution device 300 relays signals sent and received between lobby station 100 and room monitor 200 .

In the following description, the direction from the lobby station 100 to the indoor monitor 200 is called "downlink", and the packets and signals transmitted in the downlink are called "downlink packet" and "downlink signal", respectively. The direction from the indoor monitor 200 to the lobby station 100 is called "uplink direction", and the packets and signals transmitted in the uplink direction are called "uplink packets" and "uplink signals", respectively.

<Frame format, time slot format>
Next, the frame format and time slot format according to this embodiment will be explained using FIG. As shown in FIG. 2, each frame has an area of 12000 bits, a period of 10 ms and a bit rate of 2.4 Mbps, and is divided into 12 time slots from "SL0" to "SL11". Therefore, each time slot has an area of 2000 bits=250 bytes, a period of 0.833 μsec, and a bit rate of 2.4 Mbps.

“SL1” to “SL8” are time slots assigned for video data transmission from the lobby station 100 . "SL9" to "SL11" are reserved slots, and may be used as time slots for voice data or commands.

If it is necessary to synchronize data transmission between the lobby station 100 and the room monitor 200, "SL0" may be used as a control slot (beacon).

Each time slot is divided into a 53-byte guard space, a 6-byte preamble field (Preamble), a 1-byte sync field (Sync), an 8-byte control data field, a maximum 180-byte variable length user data field, and a 2-byte checksum field. there is

A guard space is a period provided between time slots for command execution such as initial reset when each time slot is received. Preamble data having a predetermined unique pattern is written in the preamble field.

A predetermined sync pattern is written in the sync field. A sync pattern is a known data string placed in a sync field, used to establish synchronization when receiving data, and used to confirm that the received data has been received at the correct timing. data pattern.

Control data indicating the data length of the user data in the user data field is written in the control data field. The remainder of the control data field is reserved space for the future. User data is written in the user data field. A checksum, which is a type of error detection code, is written in the checksum field. In the following description, control data, user data and checksum may be simply referred to as "data part". The configuration of the data section is an example, and the configuration may be different depending on the signal processing.

In this way, when data is transmitted in the “downstream direction” from the lobby station 100 to the indoor monitor 200 via the distribution device 300 using a communication frame composed of a plurality of time slots, video data, audio Data and command data can be assigned to each slot and time division multiplexed. In this case, only video data, video data and audio data, or video data, audio data, and command data can be transmitted.

When data is transmitted in the "downstream direction" using a communication frame composed of multiple time slots, at least one time slot should be allocated for video data according to system requirements such as the amount of data. good. Similarly, when transmitting video data and audio data, at least one time slot should be assigned for video data and at least one time slot should be assigned for audio data.

<Configuration of Lobby Station>
Next, the configuration of lobby station 100 will be described with reference to FIG. In FIG. 3, the lobby station 100 has a terminal T131 for connection with the distribution device 300-1.

As shown in FIG. 3, the lobby station 100 mainly includes a key input unit 101, a speaker 102, a microphone 103, a camera module 104, a control unit 105, a digital modulation unit 106, and a command modulation/demodulation unit 107. , an analog audio processing unit 108 and a storage unit 109 . The control unit 105 has a crystal oscillation unit 142 inside. Digital modulation section 106 has binary level conversion section 151 and binary VF conversion section 152 therein. The lobby station 100 also has a digital modulation signal pass filter F101, a command signal pass filter F102 and an audio signal pass filter F103.

As shown in FIG. 4, the key input unit 101 has various buttons including key numbers assigned to the respective indoor monitors 200, and transmits a signal indicating the key number and a call instruction signal to the control unit 105 in response to button operation. Output. Note that the key numbers are not limited to numbers corresponding to physical keys on a one-to-one basis as shown in FIG. 4, but may be numbers corresponding to a combination of a plurality of keys, such as room numbers.

The speaker 102 converts the analog audio signal output from the analog audio processing unit 108 into audio and outputs the audio. Microphone 103 collects surrounding sounds, converts them into analog sound signals, and outputs them to analog sound processing section 108 .

The camera module 104 includes a digital camera, shoots an object to generate digital video data, and uses H.264. The video data is sequentially compressed according to the moving picture compression standard such as H.264. The compressed digital video data is output to control section 105 .

The control unit 105 generates various command data. For example, when a signal indicating a key number and a call instruction signal are input from key input unit 101, control unit 105 inputs a source ID (identifier of lobby station 100) and a destination ID (identifier of indoor monitor 200 of the communication partner). Generate command data for calls containing Then, control section 105 outputs the command data to command modem section 107 . Also, the control section 105 controls each section of the lobby station 100 based on the content of the command data input from the command modem section 107 . For example, when video-related command data is input, the control unit 105 controls the imaging range, backlight correction, and the like in the camera module 104 .

The control unit 105 also divides the digital video data output from the camera module 104 as appropriate, and writes the divided data into user data fields of predetermined time slots (“SL1” to “SL8”). Also, the control unit 105 writes the data length of the user data written in the user data field of each time slot into the control data field of each time slot. Further, control section 105 writes preamble data and a sync pattern in each time slot. Through these processes, the control unit 105 generates a downstream packet (transmission data). The control section 105 outputs the digital data string of the downstream packet to the digital modulation section 106 .

The digital modulation unit 106 digitally modulates the digital data string of the downstream packet output from the control unit 105 . Digital modulation is a modulation method that modulates a carrier wave (carrier) discontinuously. Typical digital modulation methods include FSK modulation (Frequency Shift Keying), ASK modulation (Amplitude Shift Keying), PSK modulation (Phase Shift Keying), and the like. In this embodiment, a case of using FSK modulation will be described.

The binary level conversion unit 151 of the digital modulation unit 106 converts the H (High) level of the digital data string into a first voltage value, and converts the L (Low) level into a second voltage value.

The binary VF converter 152 of the digital modulator 106 outputs carrier waves with carrier frequencies corresponding to the first voltage value and the second voltage value. As a result, an FSK modulated waveform is generated in which the H level is the first carrier frequency (eg, 13 MHz) and the L level is the second carrier frequency (eg, 9 MHz). The FSK-modulated carrier wave (hereinafter also referred to as “digital modulated signal”) is transmitted to the indoor monitor 200 via the distribution device 300 after passing through the digital modulated signal pass filter F101.

Command modulation/demodulation section 107 ASK-modulates the command data output from control section 105 to obtain a command signal. The command signal is transmitted to the distribution device 300 after passing through the command signal pass filter F102. Command modulation/demodulation section 107 ASK-demodulates the command signal transmitted from distribution apparatus 300 and passed through command signal pass filter F102, and outputs command data to control section 105. FIG.

The analog audio processing unit 108 performs analog audio processing such as amplification on the analog audio signal output from the microphone 103 . The analog audio signal is transmitted to the indoor monitor 200 via the distribution device 300 after passing through the audio signal pass filter F103. Further, the analog audio processing unit 108 performs processing such as amplification on the analog audio signal that is transmitted from the indoor monitor 200, passes through the distribution device 300, and has passed through the audio signal pass filter F103, and outputs the amplified audio signal to the speaker 102.

The storage unit 109 is used by the control unit 105 as a work area when executing various programs. Further, the storage unit 109 stores in advance various application programs and various software programs to be executed by the control unit 105 . Note that the storage unit 109 is also used as a memory for various settings and data to be held.

In the lobby station 100, an AC adapter converts commercial alternating current power into direct current power, which is supplied to each unit. Although the AC adapter is external, the lobby station 100 may have a built-in power supply. Lobby station 100 may also have a simple display.

The digital modulated signal pass filter F101 is a filter whose pass band is a frequency band (for example, from 8.5 MHz to 14 MHz) used for communication of digital modulated signals.

The command signal pass filter F102 is a filter whose pass band is a frequency band (for example, 300 kHz±30 kHz) used for command signal communication.

The audio signal pass filter F103 is a filter whose pass band is a frequency band (for example, from 270 Hz to 3.3 kHz) used for communication of audio signals.

<Indoor monitor configuration>
Next, the configuration of indoor monitor 200 will be described with reference to FIG. The indoor monitor 200 has a terminal T231 for connection with the distribution device 300. FIG.

As shown in FIG. 5, the indoor monitor 200 mainly includes a digital demodulation unit 201, a received data processing unit 202, a control unit 203, a key input unit 204, a video data processing unit 205, and a display unit 206. , a command modulation/demodulation unit 207 , an analog audio processing unit 208 , a speaker 209 , a microphone 210 , a DC power supply unit 211 , an incoming call detection unit 212 , and a storage unit 213 . The digital demodulator 201 has a binary FV converter 251 and a binary level converter 252 inside. The control unit 203 has a crystal oscillation frequency control unit 241 and a crystal oscillation unit 242 inside. In addition, the indoor monitor 200 includes a digital modulated signal pass filter F201, a digital modulated signal pass filter F202, a command signal pass filter F203, a command signal pass filter F204, an audio signal pass filter F205, an audio signal block filter F206, and a DC command pass filter 207. have

The digital demodulator 201 digitally demodulates (FSK demodulates) the carrier wave (digital modulated signal) transmitted from the lobby station 100, passed through the distribution device 300 and passed through the digital modulated signal pass filter F201, and converts it into a digital data string of downstream packets. get Digital demodulation section 201 outputs a digital data string to reception data processing section 202 .

The binary FV converter 251 of the digital demodulator 201 converts the carrier wave of the first carrier frequency into a first voltage value, and converts the carrier wave of the second carrier frequency into a second voltage value.

The binary level converter 252 of the digital demodulator 201 converts the first voltage value to H level, converts the second voltage value to L level, and obtains a downstream packet digital data string.

The received data processing unit 202 performs digital signal processing corresponding to the input format of the control unit 203 on the digital data string output from the digital demodulation unit 201 and outputs the result to the control unit 203 .

Control section 203 detects synchronization with lobby station 100 (timing at the beginning of each bit of the received data) using preamble data and sync pattern included in the downstream packet input from received data processing section 202 . In addition, the control unit 203 extracts and reassembles the video data decomposed and written into each time slot for video data in the downlink communication frame, and outputs the regenerated video data to the video data processing unit 205. . The video data processing unit 205 performs image processing for LCD display on the screen of the display unit 206 and outputs the processed image to the display unit 206 .

Also, the control unit 203 generates various command data. For example, when receiving an incoming call detection signal from the incoming call detection unit 212, the control unit 203 generates response command data. Then, control section 203 outputs the command data to command modem section 207 . Also, the control section 203 controls each section of the indoor monitor 200 based on the content of the command data input from the command modem section 207 .

Further, when a user's monitor request is input from the key input unit 204 , the control unit 203 supplies power to the DC power supply unit 211 . Further, when receiving an incoming call detection signal from the incoming call detection unit 212, the control unit 203 performs processing (lamp lighting, chime sound, etc.) for informing the user of the incoming call.

A crystal oscillation frequency control unit 241 of the control unit 203 controls the oscillation frequency of the crystal oscillation unit 242 . The crystal oscillation unit 242 of the control unit 203 has a crystal oscillator and finely adjusts the oscillation frequency based on the control of the crystal oscillation frequency control unit 241 . The details of the configuration of the crystal oscillation frequency control section 241 and the crystal oscillation section 242 will be described later.

A key input unit 204 has various buttons, and outputs user instructions based on button operations to the control unit 203 . Note that the key input unit 204 may be a touch panel.

The video data processing unit 205 performs image processing on the video data output from the control unit 203 for LCD display on the screen of the display unit 206 , and outputs the video data after the image processing to the display unit 206 . The display unit 206 displays the video data output from the video data processing unit 205 on the screen.

Command modulation/demodulation section 207 ASK-demodulates the command signal transmitted from distribution apparatus 300 and passed through digital modulation signal blocking filter F202 and command signal passing filter F203, and outputs command data to control section 203. FIG. Also, the command modulation/demodulation unit 207 ASK-modulates the command data output from the control unit 203 to obtain a command signal. The command signal is transmitted to the distribution device 300 after passing through the command signal pass filter F203 and the digital modulation signal cutoff filter F202.

The analog audio processing unit 208 amplifies the analog audio signal that is transmitted from the lobby station 100, passes through the distribution device 300, and passes through the digital modulation signal blocking filter F202, the command signal blocking filter F204, and the audio signal passing filter F205. and other analog audio processing, and output to the speaker 209 . Also, the analog audio processing unit 208 performs analog audio processing such as amplification on the analog audio signal output from the microphone 210 . The analog audio signal passes through audio signal pass filter F205, command signal blocking filter F204 and digital modulation signal blocking filter F202, and is transmitted to lobby station 100 via distribution device 300. FIG.

The speaker 209 converts the analog audio signal output from the analog audio processing unit 208 into audio and outputs the audio. The microphone 210 collects surrounding sounds, converts them into analog sound signals, and outputs them to the analog sound processing unit 208 .

Upon receiving a monitor request from the control unit 203 , the DC power supply unit 211 transmits a monitor request (DC command) to the distribution device 300 by starting DC power supply. The DC command is transmitted to the distribution device 300 after passing through the DC command pass filter F207, the audio signal blocking filter F206, the command signal blocking filter F204 and the digital modulated signal blocking filter F202.

The incoming call detection unit 212 receives a call from the lobby station 100 and is processed by the distribution device 300, and the incoming call passes through the digital modulated signal blocking filter F202, the command signal blocking filter F204, the voice signal blocking filter F206 and the DC command passing filter F207. to detect. Then, incoming call detecting section 212 outputs an incoming call detection signal indicating that an incoming call has been detected to control section 203 .

The storage unit 213 is used by the control unit 203 as a work area when executing various programs. Further, the storage unit 213 stores in advance various application programs and various software programs executed by the control unit 203 . It is also used as a memory for various settings and data to be held.

In the indoor monitor 200, the AC adapter converts commercial AC power into DC power, which is supplied to each part. Although the AC adapter is external, the indoor monitor 200 may have a built-in power supply.

The digital modulated signal pass filter F201 is a filter whose pass band is a frequency band (for example, from 8.5 MHz to 14 MHz) used for communication of digital modulated signals.

The digital modulated signal blocking filter F202 cuts off the frequency band of the digital modulated signal (eg, 8.5 MHz to 14 MHz), and the frequency band lower and higher than the frequency band used for communication of the digital modulated signal (eg, 8.5 MHz). below and above 14 MHz).

The command signal pass filter F203 is a filter whose pass band is the frequency band (for example, 300 kHz±30 kHz) used for command signal communication.

The command signal blocking filter F204 cuts off the frequency band of the command signal (for example, 300 kHz ± 30 kHz), and the pass band is a band lower and higher than the frequency band used for command signal communication (for example, 270 kHz or lower and 330 kHz or higher). is a filter for

The audio signal pass filter F205 is a filter whose pass band is a frequency band (for example, from 270 Hz to 3.3 kHz) used for communication of audio signals.

The audio signal blocking filter F206 blocks a frequency band (for example, from 270 Hz to 3.3 kHz) used for audio signal communication, and cuts a lower band and a higher frequency band (for example, 270 Hz or lower) than the frequency band used for audio signal communication. and 3.3 kHz or more).

The DC command pass filter F207 is a filter whose pass band is the frequency band (for example, from 0 Hz to 30 Hz) used for DC command communication.

<Structure of distributor>
Next, the configuration of distribution device 300 will be described with reference to FIG. In FIG. 6, the distribution device 300 has four terminals T321, T322, T323, and T324 for connection with the indoor monitors 200, and can simultaneously connect up to four indoor monitors 200. Indicates the case of communicating with Further, the distribution device 300 has a terminal T331 for connection with the lobby station 100 or the distribution device 300 in the preceding stage, and a terminal T332 for connection with the distribution device 300 in the subsequent stage.

Also, hereinafter, a command signal (command data) communicated between the distribution device 300 and the lobby station 100 or the preceding/subsequent distribution devices 300 will be referred to as command signal A (command data A). A command signal (command data) communicated between the distribution device 300 and the indoor monitor 200 is called a command signal B (command data B).

As shown in FIG. 6, the distribution device 300 includes a digital modulation signal correction unit 301, command modulation/demodulation units 302 and 303, a control unit 304, a monitor request detection unit 305, a storage unit 306, and a calling signal generation unit. A unit 307 , a first relay 309 , a second relay 310 , a third relay 311 , and a DIP (Dual In-line Package) switch 312 . The third relays 311 and DIP switches 312 are provided as many as the number of connected indoor monitors 200 ("4" in FIG. 6). The distribution device 300 also has a digital modulation signal pass filter F301, command signal pass filters F302 and F303, and an audio signal pass filter F304.

If the carrier wave of the digital modulated signal transmitted from the lobby station 100 and passed through the first relay 309 and the digital modulated signal pass filter F301 is attenuated in the two-wire cable, the digital modulated signal correction unit 301 corrects the carrier wave. Amplify. The digital modulated signal is sent to the indoor monitor 200 via the third relay 311 .

Command modulation/demodulation section 302 ASK-demodulates command signal A which is input from lobby station 100 or pre-/post-stage distribution device 300 and has passed through command signal pass filter F302, and outputs command data A to control section 304. FIG. Command modem section 302 also ASK-modulates command data A output from control section 304 to obtain command signal A. FIG. After passing through the command signal pass filter F302, the command signal A is sent to the lobby station 100 or the pre-/post-stage distribution device 300. FIG.

Command modulation/demodulation section 303 ASK-demodulates command signal B which is input from indoor monitor 200 and which has passed through command signal pass filter F303, and outputs command data B to control section 304. FIG. Also, command modulation/demodulation section 303 ASK-modulates command data B output from control section 304 to obtain command signal B. FIG. The command signal B is transmitted to the indoor monitor 200 after passing through the command signal pass filter F303.

The control unit 304 generates various command data. For example, when receiving a monitor detection signal from the monitor request detection unit 305, the control unit 304 generates command data A for a connection request. Then, control section 304 outputs command data A for lobby station 100 to command modulation/demodulation section 302 and outputs command data B for indoor monitor 200 to command modulation/demodulation section 303 . Also, the control section 304 controls each section of the distribution apparatus 300 based on the contents of the command data A input from the command modulation/demodulation section 302 and the contents of the command data B input from the command modulation/demodulation section 303 .

Further, the control unit 304 controls the first relay 309, the second relay 310, and the third relay 311 based on the result of comparison between the key number included in the call command data and the key number stored in the storage unit 306. do. Further, the control unit 304 controls the first relay 309 , the second relay 310 and the third relay 311 when the monitor detection signal is input from the monitor request detection unit 305 . Details of the relay control of the control unit 304 will be described later.

In addition, control section 304 outputs a call instruction signal to calling signal generating section 307 at the timing of calling.

A monitor request detection unit 305 detects a monitor request (DC command) from the indoor monitor 200 . Then, the monitor request detection unit 305 outputs to the control unit 304 a monitor detection signal indicating that the monitor request has been detected and a signal specifying the indoor monitor 200 that requested the monitor.

The storage unit 306 is used by the control unit 304 as a work area when executing various programs. Further, the storage unit 306 stores in advance various application programs and various software programs executed by the control unit 304 . In particular, the storage unit 306 associates and stores the key number of the lobby station 100 assigned to each indoor monitor 200 and the terminal number of the indoor monitor connection terminal.

When a call instruction signal is input, the call signal generator 307 connects a switch to short-circuit the DC voltage between two lines (for example, 0 V), thereby generating a call signal ( DC trigger).

The first relay 309 , the second relay 310 and the third relay 311 all switch connection/disconnection under the control of the control unit 304 . In the standby state, all of the first relay 309, the second relay 310 and the third relay 311 are disconnected (see FIG. 6).

Each DIP switch 312 is set corresponding to the key number of the lobby station 100 corresponding to the indoor monitor 200 to which the third relay 311 is connected.

In distribution device 300 , the audio signal is transmitted to indoor monitor 200 via second relay 310 , audio signal pass filter F<b>304 and third relay 311 . Further, in the distribution device 300, the AC adapter converts commercial AC power into DC power, which is supplied to each unit. Although the AC adapter is external, the distribution device 300 may have a built-in power supply. Further, in each distribution device 300, DC power may be supplied from the distribution device 300 in the previous stage.

The digital modulated signal pass filter F301 is a filter whose pass band is a frequency band (for example, from 8.5 MHz to 14 MHz) used for communication of digital modulated signals.

The command signal pass filters F302 and F303 are filters whose pass band is the frequency band (for example, 300 kHz±30 kHz) used for command signal communication.

The audio signal pass filter F304 is a filter whose pass band is a frequency band (for example, from 270 Hz to 3.3 kHz) used for communication of audio signals.

<Relay control of distributor>
Next, details of relay control by the control unit 304 of the distribution device 300 will be described with reference to FIG. Note that in the standby state, the first relay 309, the second relay 310 and the third relay 311 are disconnected.

When control unit 304 receives call command data A from lobby station 100 or distribution device 300 in the preceding stage (ST501: YES), does control unit 304 match any of the key numbers of indoor monitor 200 stored in storage unit 306? It is determined whether or not (ST502).

If the key numbers do not match (ST502: NO), control section 304 determines that indoor monitor 200, which is the communication partner, is connected via another distribution device 300, and first relay 309 and second relay 310 And the third relay 311 is not controlled and the standby state is maintained.

On the other hand, if the key numbers match (ST502: YES), control section 304 determines that indoor monitor 200 of the communication partner is connected to itself, connects first relay 309 (ST504), and connects second relay 309 (ST504). The relay 310 is connected (ST505), and the third relay 311 is connected to the terminal corresponding to the matched key number (ST506). As a result, a communication path between the indoor monitor 200 of the communication partner and the lobby station 100 can be opened via the distribution device 300 .

When the monitor detection signal is input from monitor request detection section 305 (ST501: NO, ST503: YES), control section 304 connects first relay 309 (ST504) and connects second relay 310 (ST505). ), the third relay 311 is connected to the terminal of the wiring that detected the monitor request (ST506). As a result, a communication path between the indoor monitor 200 of the communication partner and the lobby station 100 can be opened via the distribution device 300 .

When neither the incoming call signal nor the monitor request signal is input (ST501: NO, ST503: NO), control section 304 does not control first relay 309, second relay 310 and third relay 311. Stay on standby.

<Requirements for Crystal Oscillation Frequency>
Next, the requirements for the crystal oscillation frequency of this embodiment will be described with reference to FIG.

When a time slot of data generated by sampling with a clock generated based on the crystal oscillation frequency of the equipment on the transmitting side is sampled with a clock generated based on the crystal oscillation frequency of the equipment on the receiving side, this embodiment is a system that resynchronizes with the 1st bit of the sync pattern in the time slot, so 1528 bits from the 1st bit of the sync pattern in the same time slot (= (1 + 8 + 180 + 2) x 8) In the data of the last bit after that, the shift of the clock on the receiving side with respect to the clock on the transmitting side becomes maximum. In this system, resynchronization is performed with the first bit of the sync pattern in the next time slot.

Here, as a system requirement, the allowable range of clock deviation when sampling 1528-bit data of the time slot is, for example, up to 1/5 (before and after 1/10) of 1-bit data length, that is, ±65 ppm ( = 1/1528 x 1/5 x 1/2). When the clock on the transmitting side is used as a standard, the receiving side device can decode the received data if the crystal oscillation frequency on the receiving side is adjusted so that the deviation of the clock on the receiving side is always within ±65 ppm. .

Therefore, in the present embodiment, as shown in FIG. 7, the time difference 603 between the transmission side data time 601 and the reception side measurement time 602 is detected with a specified number of data (for example, the number of data for 100 frames), The crystal oscillation frequency on the receiving side is adjusted according to the time difference. The transmission-side data time 601 is a time (first time) occupied by a prescribed number of pieces of transmission data sampled with a communication clock generated based on the crystal oscillation frequency of the transmission-side device. The measured time 602 on the receiving side is a time (second time) corresponding to the specified number of data counted by the communication clock generated based on the crystal oscillation frequency of the receiving side device.

Here, it is assumed that the data string of the lobby station 100 is used as the data on the transmitting side, which is the reference time, and the data string generated by the indoor monitor 200 is the data string of the receiving side, which is the comparison time.

In one time slot or one frame (12 time slots), when trying to detect the time difference between the data time on the transmitting side and the measurement time on the receiving side, the accumulated difference is small and the time difference is short. A high-speed clock is required.

Moreover, in the present embodiment, the minimum range of the adjustment width is determined in advance according to system requirements, such as MAX±5 ppm. The minimum range of adjustment width determines the frequency of the measurement clock for detecting the time difference.

<Internal Configuration of Crystal Oscillation Frequency Control Unit>
Next, details of the internal configuration of the crystal oscillation frequency control section 241 of the indoor monitor 200 will be described with reference to FIG. As shown in FIG. 8, the crystal oscillation frequency control unit 241 includes a measurement clock generation unit 281, a transmission side data time measurement unit 282, a reception side internal time measurement unit 283, a reception side time difference calculation unit 284, and an adjustment value setting unit 285. have

The measurement clock generation unit 281 generates a measurement clock having a frequency (for example, 48 MHz) based on the minimum range of the adjustment width based on the crystal oscillation frequency of the crystal oscillation unit 242, and the reception side internal time measurement unit 283 and the transmission It continuously outputs the clock for measurement to the side data time measurement unit 282 . Here, the frequencies of the measurement clock and the communication clock are both known values generated based on the crystal oscillation frequency of the receiving device, and the frequency of the measurement clock is equal to the frequency of the communication clock. can be

The transmission-side data time measurement unit 282 measures the time (the time from the count start point to the count end point of the received data) occupied by the specified number of data in the received signal (hereinafter referred to as "reference time"). This reference time corresponds to the time (601 in FIG. 7) occupied by the specified number of transmission data sampled by the communication clock generated based on the internal oscillation frequency of the lobby station 100, which is the device on the transmission side. .

The receiving-side internal time measuring unit 283 converts the time corresponding to the prescribed number of data counted by the communication clock into the count number of the measuring clock, and counts the measuring clock output from the measuring clock generating unit 281. From the start point, the number corresponding to the prescribed number of data is counted, and the time (602 in FIG. 7) from the start to the end of counting the clock for measurement (hereinafter referred to as "comparison time") is measured. Note that there is no particular limitation on the count start point in the transmitting side data time measuring section 282 and the receiving side internal time measuring section 283 .

The receiving side time difference calculating section 284 calculates the difference (603 in FIG. 7) between the reference time measured by the transmitting side data time measuring section 282 and the comparison time measured by the receiving side internal time measuring section 283 .

The adjustment value setting unit 285 stores a setting value corresponding to the time difference calculated by the reception side time difference calculation unit 284 in the register 299 (see FIG. 9) of the crystal oscillation unit 242 in order to reduce the deviation between the reference time and the comparison time. set and adjust the oscillation frequency of the crystal oscillator 242 . Note that the adjustment value setting unit 285 may stop adjusting the oscillation frequency when the time difference calculated by the reception-side time difference measuring unit 284 is equal to or less than a predetermined threshold. Also, the threshold may have hysteresis.

The adjustment value setting unit 285 causes the storage unit 213 to store the setting value corresponding to the oscillation frequency of the crystal oscillation unit 242 that was adjusted at the time of the last call for each indoor monitor 200 . The adjustment value setting unit 285 calls up the setting value stored in the storage unit 213 and sets it in the register 299 as a new initial setting value at the next call.

It is assumed that the crystal oscillation frequency of the lobby station 100 and the crystal oscillation frequency of the indoor monitor 200 have been adjusted to the center values at the time of shipment from the factory.

In this embodiment, the adjustment operation of the crystal oscillation frequency in the lobby station 100 and the indoor monitor 200 can be performed in the background in parallel with the received data processing during normal operation. As a result, there is no need to set a time for adjustment, and high-precision digital communication can be performed within the variation range of initial adjustment in which bit errors in received data do not occur in normal reception operations.

<Internal configuration of crystal oscillator>
Next, details of the internal configuration of the crystal oscillator 242 of the indoor monitor 200 will be described with reference to FIG. As shown in FIG. 9, the crystal oscillator 242 includes a crystal oscillator 290 (oscillating frequency X1), an inverter 291, a feedback resistor 292 (resistance value Rf), a damping resistor 293 (resistance value Rd), a buffer 294, an input capacitor 295 (capacitance value C2) and an output capacitor 296 (capacitance value C3), an input capacitor 297 (capacitance value C1), an output capacitor 298 (capacitance value C4), and a register 299 are added to the general CMOS inverter crystal oscillator circuit. take.

A capacitance value C 1 of the input capacitance 297 and a capacitance value C 4 of the output capacitance 298 are set in advance to be specified values corresponding to the initial values of the register 299 .

When a new value is set in the register 299 by the crystal oscillation frequency control unit 241 (adjustment value setting unit 285), the capacitance value C1 of the input capacitance 297 or the capacitance value C4 of the output capacitance 298 is adjusted according to this value. be. As a result, the oscillation frequency of the crystal oscillator 242 is finely adjusted to match the crystal oscillation frequency of the indoor monitor 200 on the transmission side.

Although the internal configuration of the crystal oscillator 242 of the indoor monitor 200 has been described here, the internal configuration of the crystal oscillator 142 of the lobby station 100 is the same. The frequency adjustment of the crystal oscillation unit 142 of the lobby station 100 is used when it is adjusted to the center value by register setting at the time of shipment from the factory.

<Sequence from standby state to communication state>
Next, the sequence from the standby state to the communication state according to this embodiment will be described with reference to FIGS. 11 and 12. FIG.

FIG. 11 shows the sequence for activation by the lobby station 100 . When the call button of the lobby station 100 is pushed down (S702) in a standby state in which data is not transmitted/received between devices (S701), the lobby station 100 transmits call command data A to the distribution device 300. (S703).

When the call command data A matches one of the key numbers of the indoor monitor 200 stored in the storage unit 306, the distribution device 300 connects the first relay 309 and the second relay 310 to The third relay 311 is connected to the terminal corresponding to the key number (S704). As a result, a communication path between the indoor monitor 200 of the communication partner and the lobby station 100 can be opened via the distribution device 300 . After the communication path between the lobby station 100 and the indoor monitor 200 is secured, fine adjustment of the crystal oscillation frequency of the crystal oscillator 242 of the indoor monitor 200 is performed.

Then, the distribution device 300 transmits a calling signal (DC trigger) to the connected indoor monitor 200 (S705).

The indoor monitor 200 captures the call signal transferred from the distribution device 300 (S706), and transmits response command data B to the distribution device 300 (S707).

When the distribution device 300 receives the response command data B from the indoor monitor 200, it transmits the response command data A to the lobby station 100 (S708).

When the lobby station 100 receives the response command data A, the lobby station 100, the distribution device 300 and the indoor monitor 200 enter a communication state (S709).

Thereafter, lobby station 100 transmits video data and audio data to indoor monitor 200 via distribution device 300 (S710), and indoor monitor 200 transmits audio data to lobby station 100 via distribution device 300. (S711).

FIG. 12 shows the sequence for activation by the indoor monitor 200 . In a standby state in which data is not transmitted/received between devices (S801), when a monitor request operation is performed with the key input unit 204 of the indoor monitor 200 (S802), the indoor monitor 200 sends a monitor request (DC command) is transmitted (S803).

When the distribution device 300 receives the monitor request, it connects the first relay 309 and the second relay 310, and connects the third relay 311 to the terminal corresponding to the matching key number (S804). As a result, a communication path between the indoor monitor 200 of the communication partner and the lobby station 100 can be opened via the distribution device 300 . After the communication path between the lobby station 100 and the indoor monitor 200 is secured, fine adjustment of the crystal oscillation frequency of the crystal oscillation unit 142 of the lobby station 100 is performed.

Then, the distribution device 300 transmits the connection request command data A to the lobby station 100 (S805).

The lobby station 100 captures command data A of the connection request received from the distribution device 300 (S806), and transmits command data A of the connection response to the distribution device 300 (S807).

When the distribution device 300 receives the connection response command data A from the lobby station 100, the distribution device 300 transmits the connection response command data B to the indoor monitor 200 (S808).

When the indoor monitor 200 receives the connection response command data B, the lobby station 100, the distribution device 300, and the indoor monitor 200 enter a communication state (S809), and monitoring of audio data and video data from the lobby station 100 is started. becomes possible (S810).

<Frequency band of each signal>
Next, the frequency band of each signal transmitted and received by the intercom system 1 will be explained in comparison with that of the conventional analog system.

In an analog intercom system, as shown in FIG. 13A, uplink and downlink DC commands, uplink and downlink analog audio signals, uplink and downlink ASK commands, and downlink analog video signals are in different frequency bands. sent and received by

In the example of FIG. 13A, the DC command uses 0 Hz (direct current component), the analog audio signal is transmitted and received in a frequency band from 300 Hz to about 3 kHz, the ASK command is transmitted and received at a frequency of, for example, 300 kHz, and the analog video signal is It is transmitted and received in a frequency band from about 8.5 MHz to 14 MHz. In this way, the DC command, analog audio signal, ASK command, and analog video signal are transmitted in different frequency bands (frequency division multiplexed).

On the other hand, the intercom system 1 according to the present embodiment, as shown in FIG. 13B, receives uplink and downlink DC commands, uplink and downlink analog audio signals, uplink and downlink ASK commands, and downlink digital video data. Digitally modulated carrier waves (digital modulated signals) are transmitted and received in different frequency bands.

In the example of FIG. 13B, the DC command uses 0 Hz (direct current component), the analog audio signal uses a frequency band from 300 Hz to 3 kHz, the ASK command uses a frequency band of 300 kHz, and the carrier wave (digital modulation signal) is For example frequencies of 9 MHz and 13 MHz, which are within the conventional analog video signal band, are used. Note that the numerical values of each frequency band in FIG. 13B are merely examples, and the present embodiment is not limited to these numerical values. The carrier wave (digital modulated signal) of the intercom system 1 according to the present embodiment may use a frequency within the analog video signal band of the switchable conventional analog intercom system.

As is clear from the comparison between FIGS. 13A and 13B, the frequencies (bands) of the DC command, analog audio signal, and ASK command in intercom system 1 according to the present embodiment are the same as those in the analog intercom system. be. Further, the binary frequency of the carrier wave (digital modulated signal) in the intercom system 1 according to the present embodiment is within the range of the frequency band used for transmitting and receiving the analog video signal.

Therefore, in the intercom system of the present embodiment, the frequency band passed/blocked by the filter can be shared with that of the conventional analog intercom system. Therefore, when switching from the analog system to the digital system (this embodiment), the filters used in each device (lobby station, room monitor) of the analog door phone system can be used as they are. In addition, the two-wire cable and distribution device of the analog door phone system can be used as they are.

<effect>
As described above, in the present embodiment, compression processing is performed on digital video data, and digital modulation is performed on the compressed digital video data. As a result, if the binary frequency of the carrier wave (digital modulated signal) is set within the range of the frequency band used for transmission and reception of the analog video signal, the analog intercom system can be used when switching from the analog system to the digital system. The filters used in each device (lobby station, room monitor) can be used as they are. In addition, the two-wire cable and distribution device of the analog door phone system can be used as they are. As described above, according to the present embodiment, when switching from the analog system to the digital system, much of the existing equipment can be used as is without adding a new device. In particular, since the two-wire cable and the distribution device can be used as they are, there is no need to redo the wiring work in the wall, the switching work is greatly simplified, and the labor and cost can be greatly reduced.

(Embodiment 2)
In the second embodiment, since there are some changes to the lobby station 100 and the room monitor 200 described in the first embodiment, the lobby station 100A and the room monitor 200A are hereinafter referred to. Note that the system configuration of this embodiment is the same as that in FIG. 1 described in the first embodiment, so the description is omitted. Also, the configuration of the distribution device 300 of the present embodiment is the same as that of FIG. 6 described in the first embodiment, so description thereof will be omitted.

<Configuration of Lobby Station>
Next, the configuration of the lobby station 100A of this embodiment will be described using the block diagram of FIG. In the lobby station 100A shown in FIG. 14, the same components as in the lobby station 100 shown in FIG. 3 are denoted by the same reference numerals as in FIG. 3, and descriptions thereof are omitted. Lobby station 100A differs from lobby station 100 in that voice data processing section 121 is added and functions of control section 105 and analog voice processing section 108 are changed.

The audio data processing unit 121 performs A/D (Analog/Digital) conversion on the analog audio signal output from the microphone 103 to generate digital audio data. G. It may be encoded with an audio codec such as G.726. The digital audio data is output to control section 105 .

The control unit 105 writes the digital audio data output from the audio data processing unit 121 into the user data field of a predetermined time slot (for example, "SL9"). Note that other functions of the control unit 105 are common to those described in the first embodiment.

The analog audio processing unit 108 receives an upstream analog audio signal and outputs the analog audio signal that has undergone analog audio processing such as amplification to the speaker 102 .

<Indoor monitor configuration>
Next, the configuration of the indoor monitor 200A of this embodiment will be described using the block diagram of FIG. In addition, in the indoor monitor 200A shown in FIG. 15, the same components as in the indoor monitor 200 shown in FIG. 5 are given the same reference numerals as in FIG. Compared with the indoor monitor 200, the indoor monitor 200A has an audio data processing section 221 added, and the functions of the control section 203 and the analog audio processing section 208 are changed.

The control unit 203 extracts and reassembles the audio data of the audio data time slots in the downlink communication frame, and outputs the regenerated audio data to the audio data processing unit 221 . Note that other functions of the control unit 203 are common to those described in the first embodiment.

The audio data processing unit 221 performs D/A (Digital/Analog) conversion on the digital audio data output from the control unit 203 to generate an analog audio signal. G. In the case of audio data encoded by an audio codec such as G.726, the audio data processing unit 221 performs D/A conversion on the decoded audio data to generate an analog audio signal. The analog audio signal is output to speaker 209 .

The analog audio processing unit 208 performs analog audio processing such as amplification on the analog audio picked up by the microphone, and transmits it to the lobby station 100A via the distribution device 300 via the two-wire cable.

<effect>
As described above, in the present embodiment, compression processing is performed on digital video data, and digital modulation is performed on the compressed digital video data and digital audio data. As a result, if the binary frequencies of the video and audio carrier signals are set within the range of the frequency band used for transmitting and receiving analog video signals, the analog intercom system can be used when switching from the analog system to the digital system. The filters used in each device (lobby station, room monitor) can be used as they are. Also, the distributor of the analog door phone system can be used as it is. As described above, according to the present embodiment, when switching from the analog system to the digital system, many existing facilities can be used as they are without adding a new device. Further, according to the present embodiment, in addition to the video data from the lobby station 100A, the audio data can also be digitized. can be confirmed. Furthermore, according to the present embodiment, since it is possible to easily adjust the relative delay between video and audio, it is possible to prevent large shifts between video and audio on the indoor monitor 200A side.

It should be noted that the present disclosure is not limited to the above-described embodiments in terms of the type, arrangement, number, etc. of the members, and deviates from the gist of the invention, such as by appropriately replacing the constituent elements with those having equivalent effects. It can be changed appropriately as long as it does not occur.

For example, in the present disclosure, the number of distribution devices 300 and the number of indoor monitors 200 connected to each distribution device 300 are not particularly limited.

Also, in the above description, the case of using FSK modulation as a digital modulation method has been described, but the present disclosure is not limited to this, and other digital modulation such as ASK modulation, PSK modulation, etc. may be used. When ASK modulation is used, for example, the first carrier frequency is set to 13 MHz, the second carrier frequency is not modulated, and the first carrier frequency is set within the frequency band used for transmitting and receiving analog video signals. Further, when PSK modulation is used, for example, one carrier frequency is used, the carrier wave is modulated so that the H level and the L level of the digital data string are in different phases, and the carrier frequency is used to convert the analog video. Be within the frequency band used to transmit and receive signals.

INDUSTRIAL APPLICABILITY The present disclosure is suitable for use in a door phone system for collective housing.

1 door phone system 100, 100A lobby station 101, 204 key input unit 102, 209 speaker 103, 210 microphone 104 camera module 105, 203, 304 control unit 106 digital modulation unit 107, 207, 302, 303 command modulation/demodulation unit 108, 208 analog Audio processing units 109, 213, 306 Storage units 121, 221 Audio data processing units 142, 242 Crystal oscillation unit 151 Binary level conversion unit 152 Binary VF conversion unit 200, 200A Indoor monitor 201 Digital demodulation unit 202 Received data processing Unit 205 Video data processing unit 206 Display unit 211 DC power supply unit 212 Incoming call detection unit 241 Crystal oscillation frequency control unit 251 Binary FV conversion unit 252 Binary level conversion unit 300 Distribution device 301 Digital modulation signal correction unit 305 Monitor request detection Part 307 Call Signal Generation Part 309 First Relay 310 Second Relay 311 Third Relay 312 DIP Switch

Claims (8)

a lobby station, an indoor monitor, and a distribution device for relaying communication between the lobby station and the indoor monitor, wherein the lobby station transmits digital video signals and digital video signals to the indoor monitor via the distribution device. A door phone system in which a downstream audio signal is transmitted, and the indoor monitor transmits an upstream audio signal to the lobby station via the distribution device, wherein an analog lobby station different from the lobby station is connected to the distribution device. at the lobby station of the intercom system capable of transmitting an analog video signal to the distribution device within a first frequency band and transmitting a downstream audio signal within a second frequency band different from the first frequency band , There is
a camera module that captures a subject, generates digital video data, and compresses the digital video data;
a control unit that converts the compressed digital video data into packets;
a digital modulation unit that performs digital modulation on the digital data string of the packet and outputs a carrier wave of a digital modulated signal having a frequency within the first frequency band;
A lobby station with A microphone unit that converts the collected sound into an analog audio signal,
an audio modulation unit that performs analog audio processing on the analog audio signal and outputs a carrier wave of the downstream audio signal having a frequency within the second frequency band;
and
The digital video signal is division-multiplexed with the downlink audio signal,
A lobby station according to claim 1. The digital modulation unit performs FSK modulation (Frequency Shift Keying) on the digital data sequence of the packet,
A lobby station according to claim 1 or 2. The digital modulation unit performs ASK modulation (Amplitude Shift Keying) on the digital data string of the packet,
A lobby station according to claim 1 or 2. The digital modulation unit performs PSK modulation (Phase Shift Keying) on the digital data string of the packet.
A lobby station according to claim 1 or 2. The control unit
Allocating at least one time slot of a communication frame consisting of a plurality of time slots for the digital video data;
A lobby station according to any one of claims 1 to 5. a lobby station, an indoor monitor, and a distribution device for relaying communication between the lobby station and the indoor monitor, wherein an analog type lobby station different from the lobby station is connected to the distribution device as a first A door phone system capable of transmitting an analog video signal to the distribution device within a frequency band and transmitting a downstream audio signal within a second frequency band different from the first frequency band ,
said lobby station,
Take a picture of the subject and generate digital video data,
compressing the digital video data,
converting the compressed digital video data into packets;
digitally modulating the digital data sequence of the packet to generate a carrier wave of a digitally modulated signal having a frequency within the first frequency band;
transmitting the digital modulated signal and the downstream audio signal to the indoor monitor via the distribution device;
The indoor monitor
transmitting upstream audio signals to the lobby station via the distribution device;
doorphone system. a lobby station, an indoor monitor, and a distribution device for relaying communication between the lobby station and the indoor monitor, wherein an analog type lobby station different from the lobby station is connected to the distribution device as a first A communication method for a door phone system capable of transmitting an analog video signal to the distribution device within a frequency band and transmitting a downstream audio signal within a second frequency band different from the first frequency band ,
said lobby station,
Take a picture of the subject and generate digital video data,
compressing the digital video data,
converting the compressed digital video data into packets;
digitally modulating the digital data sequence of the packet to generate a carrier wave of a digitally modulated signal having a frequency within the first frequency band;
transmitting the digital modulated signal and the downstream audio signal to the indoor monitor via the distribution device;
The indoor monitor
transmitting upstream audio signals to the lobby station via the distribution device;
Communication method.

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