JP2017092701A - Intercom and communication method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve work efficiency when a construction worker installs a 2-wire cable.SOLUTION: A connection state detection section 134 of a control unit 107 determines that a 2-wire cable is normally connected when a synchronous pattern of received data is completely in accord with a synchronous pattern for normal connection check or that the 2-wire cable is inversely connected when the synchronous pattern of the received data is completely in accord with a synchronous pattern for inverse connection check. A transmission data inversion section 109 inverts an incoming signal output from a transmission data processing section 108 when the 2-wire cable is determined to be inversely connected. A received data inversion section 112 inverts an outgoing signal output from a reception driver 111 when the 2-wire cable is determined to be inversely connected.SELECTED DRAWING: Figure 3

Description

  The present disclosure relates to a child device, a parent device, a monitor of a door phone system, and a communication method of the door phone system.

  In recent years, in homes and the like, for example, a slave unit with a camera (hereinafter referred to as an “entrance slave unit”) installed at a front door outside the home, and an image captured on the monitor of the entrance slave unit camera on a monitor A door phone system comprising a main phone (hereinafter referred to as “door phone master”) is widely used. In some cases, a monitor is added to the door phone system (hereinafter referred to as “additional monitor”).

  Generally, in a door phone system, an entrance cordless handset and a door phone master phone are connected by a two-wire cable. Further, the door phone master unit and the extension monitor are connected by a two-wire cable. Patent Document 1 describes a door phone system that transmits and receives packets between an entrance cordless handset and a doorphone master set connected by a two-wire cable.

JP 2007-124227 A

  However, according to the prior art, when a construction worker reversely connects a two-wire cable at the time of initial setting, operation, and expansion of a door phone system, data cannot be demodulated by a receiving side device. For this reason, much labor is required to prevent reverse connection, and the work efficiency at the time of two-wire cable wiring is lowered.

  The objective of this indication is providing the communication method of the subunit | mobile_unit of a door phone system, a main | base station, a monitor, and a door phone system which can aim at the improvement of the working efficiency at the time of 2 wire cable wiring by a construction worker.

  The child device of the present disclosure includes the child device of the door phone system in which a parent device and a child device are connected via a two-wire cable, and packet signals are transmitted and received between the parent device and the child device by time division duplex. And, when the two-wire cable is a reverse connection or a connection state detection unit that determines whether the two-wire cable is a reverse connection, and when the two-wire cable is a reverse connection, A reception unit that performs reception processing after inversion, and a transmission unit that performs transmission processing after inversion with respect to transmission data to the base unit when the two-wire cable is reversely connected.

  The parent device of the present disclosure includes the parent device of the door phone system in which the parent device and the child device are connected via a two-wire cable, and packet signals are transmitted and received between the parent device and the child device by time division duplex. A connection state detection unit that determines whether the two-wire cable is a normal connection or a reverse connection, a reception unit that performs reception processing on reception data from a master unit of another door phone system, A transmission unit that performs transmission processing after inverting the transmission data to the master unit of the other door phone system when the two-wire cable is reversely connected.

  The monitor according to the present disclosure is added to a door phone system including a parent device and a child device, is connected to the parent device via a two-wire cable, and transmits and receives packet signals to and from the parent device by time division duplex. A monitor that detects whether the two-wire cable is a normal connection or a reverse connection; and when the two-wire cable is a reverse connection, the received data from the master unit A reception unit that performs reception processing after inversion, and a transmission unit that performs transmission processing after inverting the transmission data to the base unit when the two-wire cable is reversely connected .

  The communication method of the present disclosure is a communication method of a door phone system in which a parent device and a child device are connected via a two-wire cable, and packet signals are transmitted and received between the parent device and the child device by time division duplex. The slave unit determines whether the two-wire cable is connected in the normal direction or the reverse connection, and when the two-wire cable is connected in the reverse direction, , Performing a reception process after inversion, and if the two-wire cable is reversely connected, performing a transmission process after inverting the transmission data to the base unit, and The parent device includes a step of transmitting data to the child device via the two-wire cable and a step of receiving data from the child device via the two-wire cable.

  According to the present disclosure, when the two-wire cable is reversely connected, the transmission / reception is performed after the data is inverted in either the transmission-side device or the reception-side device, thereby affecting the connection state of the two-wire cable. The receiving device can demodulate the data. Therefore, the construction worker can wire the two-wire cable without worrying about the connection state (normal connection or reverse connection), so that the work efficiency at the time of wiring the two-wire cable can be increased.

The system block diagram which shows the structure of the door phone system which concerns on one embodiment of this indication The figure which shows the frame structure and slot structure which concern on one embodiment of this indication The block diagram which shows the structure of the entrance cordless handset which concerns on one embodiment of this indication The block diagram which shows the structure of the door phone main unit which concerns on one embodiment of this indication The block diagram which shows the structure of the expansion monitor which concerns on one embodiment of this indication The figure which shows an example of the modulation process with respect to packet data (1 bit) The figure which shows an example of the modulation process with respect to packet data (multiple bits) The figure which shows an example of the preamble data used in one embodiment of this indication The block diagram which shows the internal structure of the synchronous detection part of the entrance cordless handset which concerns on one embodiment of this indication The figure which shows an example of the synchronous detection process of the entrance cordless handset which concerns on one embodiment of this indication The flowchart which shows an example of operation | movement of the synchronous detection process which concerns on one embodiment of this indication The flowchart which shows an example of operation of the entrance cordless handset concerning an embodiment of this indication The flowchart which shows an example of operation of the door phone main unit concerning an embodiment of this indication

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

<System overview>
First, the outline | summary of the door phone system which concerns on one embodiment of this indication is demonstrated using FIG. As shown in FIG. 1, the door phone system 1 includes an entrance cordless handset 100 and a door phone master set 200. Note that FIG. 1 illustrates a case where three door slave devices 100-1, 100-2, and 100-3 are connected to the doorphone master device 200. Further, an additional monitor 300 may be added to the door phone system 1. Furthermore, the door phone system 1 can be connected to other door phone systems.

  The entrance cordless handset 100 is provided, for example, at the entrance of a house or the like. The doorphone master 200 and the extension monitor 300 are provided in a home such as a house, for example, and are fixed to a wall or placed on a table or a table. The entrance cordless handset 100 and the door phone master set 200 are connected by a two-wire cable made of a pair of copper wires. The extension monitor 300 is connected to the door phone master unit 200 by a two-wire cable.

  The intercom master device 200 communicates with the entrance slave device 100, receives video data, audio data, and control data from the entrance slave device 100, and transmits the audio data and control data. The intercom base unit 200 communicates with the expansion monitor 300, transfers the video data, audio data, and control data received from the front door unit 100 to the expansion monitor 300, and receives the audio data and control data received from the expansion monitor 300. Is transferred to the entrance cordless handset 100.

  In the following description, the direction from the entrance slave unit 100 or the extension monitor 300 to the doorphone master unit 200 is referred to as “upward direction”, and packets and signals transmitted from the entrance slave unit 100 or the extension monitor 300 in the upward direction are referred to as “upward direction”. They are called “upstream packet” and “upstream signal”, respectively. Further, the direction from the doorphone master unit 200 to the entrance slave unit 100 or the extension monitor 300 is referred to as “downward direction”, and packets and signals transmitted from the doorphone master unit 200 in the downward direction are referred to as “downstream packet” and “downstream signal”, respectively. "

<Frame configuration, slot configuration>
Next, a frame configuration and a slot configuration according to the present embodiment will be described with reference to FIG. As shown in FIG. 2, each frame has a 48000 bit area, has a 10 ms period, a 4.8 Mbps bit rate, and is divided into 24 slots. Therefore, each slot has an area of 2000 bits = 250 bytes, and has a bit rate of 0.416 ms and a bit rate of 4.8 Mbps.

  Each slot is divided into a 52-byte guard space (Guard), a 4-byte preamble field, a 2-byte sync field (Sync), a 32-byte control data field, and a 160-byte user data field.

  The guard space is a time for avoiding a slot collision due to a propagation delay time difference, clock jitter, or the like. Preamble data (described later) having a predetermined unique pattern is added to the preamble field. A predetermined sync pattern is added to the sync field. Control data is added to the control data field. Image data and audio data are added to the user data field. Here, the sync pattern is known data or a data string arranged in the sync field, and is used to establish synchronization at the time of reception data reception, and confirms that reception data has been received at an accurate timing. This is a known data pattern defined in advance.

<Configuration of entrance cordless handset>
Next, the structure of the entrance cordless handset 100 is demonstrated using the block diagram of FIG. As shown in FIG. 3, the entrance slave device 100 includes a cable connection unit 101, a key input unit 102, a speaker 103, a microphone 104, an audio I / F (interface) unit 105, a camera unit 106, and a control unit 107. The control unit 107 includes a first clock generation unit 131, a packet generation unit 132, a data reproduction unit 133, and a connection state detection unit 134 inside. Further, the front door device 100 includes a transmission data processing unit 108, a transmission data inversion unit 109, a transmission driver 110, a reception driver 111, a reception data inversion unit 112, a synchronization detection unit 113, and a second clock generation unit 114.

  The cable connection unit 101 includes a connection terminal for a two-wire cable, and connects the one end on the entrance side of the two-wire cable to the reception driver 111 and the transmission driver 110 in a state where signals can be transmitted. Note that the other end of the two-wire cable is connected to the doorphone master unit 200.

  The key input unit 102 includes a call button. When the call button is operated, the key input unit 102 outputs a signal indicating that to the control unit 107.

  The speaker 103 converts the analog audio data output from the audio I / F unit 105 into audio and outputs the audio.

  The microphone 104 collects ambient sound, converts it into analog sound data, and outputs it to the sound I / F unit 105.

  The audio I / F unit 105 converts the digital audio data output from the control unit 107 into analog audio data, adjusts the signal level, and outputs the analog audio data to the speaker 103. The audio I / F unit 105 adjusts the signal level of the analog audio data output from the microphone 104, converts the analog audio data into digital audio data, and outputs the digital audio data to the control unit 107. Such analog / digital conversion is performed by an A / D, D / A converter (not shown).

  The audio I / F unit 105 outputs data obtained by performing predetermined audio compression processing on the data obtained by digitally converting the analog audio data output from the microphone 104 to the control unit 107 as digital audio data. May be. In addition, when the digital audio data output from the control unit 107 is data obtained by performing predetermined audio compression processing, the audio I / F unit 105 performs predetermined audio expansion processing on the data. To digital / analog conversion.

  The camera unit 106 includes a digital camera, takes a video of the entrance, generates digital video data, and outputs the digital video data to the control unit 107. Note that the camera unit 106 may include an encoder module. That is, the camera unit 106 may output data obtained by performing predetermined moving image compression processing such as H.264 to the video data output from the digital camera to the control unit 107 as digital video data.

  The control unit 107 controls each part of the entrance cordless handset 100. In addition, the control unit 107 outputs a transmission control signal (SW CON) that indicates a transmission period that permits transmission and a reception period that permits reception to the transmission driver 110 and the reception driver 111.

  The first clock generation unit 131 of the control unit 107 is a clock for sampling the reception data, and the first frequency corresponding to n times (n is 1 or more) the bit rate of the reception data on the basis of the crystal oscillation. A clock (CLK) of (eg, 48 MHz (n = 10)) is generated and output to the synchronization detection unit 113 and the second clock generation unit 114.

  The packet generation unit 132 of the control unit 107 generates an uplink packet for realizing a call with video. Specifically, the packet generation unit 132 appropriately divides the digital audio data output from the audio I / F unit 105 and the digital video data output from the camera unit 106 and writes them in the user data field of each slot for control. Write data into the control data field of each slot. Furthermore, the packet generation unit 132 writes preamble data and a sync pattern in each slot, and generates an uplink packet (transmission data). Further, the packet generation unit 132 generates a transmission enable signal (SSCS) and a transmission second frequency (for example, 4.8 MHz) clock (SSCK). Then, the packet generation unit 132 outputs the uplink packet to the transmission data processing unit 108 in synchronization with the transmission enable signal (SSCS) and the clock (SSCK).

  When the data reproduction unit 133 of the control unit 107 receives the enable signal (SSCS) from the synchronization detection unit 113, the data reproduction unit 133 uses the second frequency clock (SSCK) output from the second clock generation unit 114, and receives the data inversion unit. The downlink signal output from 112 is demodulated to obtain a downlink packet. Then, the data reproduction unit 133 outputs the digital audio data included in the downlink packet to the audio I / F unit 105, and outputs the sync pattern included in the downlink packet (received data) to the connection state detection unit 134.

  The connection state detection unit 134 of the control unit 107 is a check sync pattern (hereinafter, referred to as a “positive connection check sync pattern” (for example, all 16 bits are “0”)) when the two-wire cable is connected correctly. This is a reverse pattern of the normal connection check sync pattern, and the check sync pattern when the two-wire cable is reverse connected (hereinafter referred to as “reverse connection check sync pattern” (eg, all 16 bits are “1”). )) Is remembered. Then, the connection state detection unit 134 collates the sync pattern of the reception data output from the data reproduction unit 133 with the sync pattern for the normal connection check and the sync pattern for the reverse connection check. The connection state detection unit 134 determines that the two-wire cable is correctly connected when the sync pattern of the received data completely matches the sync pattern for the normal connection check, and the sync pattern of the received data and the sync pattern for the reverse connection check If the two completely match, it is determined that the two-wire cable is reversely connected. Then, the connection state detection unit 134 outputs an inversion control signal (INV CON) indicating the determination result to the transmission data inversion unit 109 and the reception data inversion unit 112.

  When the transmission data processing unit 108 receives the enable signal (SSCS) from the packet generation unit 132, the transmission data processing unit 108 uses the second frequency clock (SSCK) output from the packet generation unit 132, and the uplink data output from the packet generation unit 132. Modulation processing is performed on the packet data to generate an uplink signal, which is output to the transmission data inverting unit 109. Details (specific example) of the modulation processing of the transmission data processing unit 108 will be described later.

  When the connection state detection unit 134 determines that the two-wire cable is reversely connected, the transmission data inversion unit 109 inverts the uplink signal output from the transmission data processing unit 108 and outputs the inverted signal to the transmission driver 110. On the other hand, when the connection state detection unit 134 determines that the two-wire cable is a normal connection, the transmission data reversing unit 109 outputs the uplink signal output from the transmission data processing unit 108 to the transmission driver 110 as it is.

  The transmission driver 110 transmits an uplink signal to the intercom base unit 200 via the cable connection unit 101 in the transmission section instructed by the switching control signal (SW CON) from the control unit 107.

  The reception driver 111 receives the downlink signal transmitted from the doorphone master device 200 via the cable connection unit 101. Then, the reception driver 111 outputs a downlink signal to the reception data inversion unit 112 in the reception period instructed by the switching control signal (SW CON) from the control unit 107.

  When the connection state detection unit 134 determines that the two-wire cable is reversely connected, the reception data inversion unit 112 inverts the downlink signal output from the reception driver 111 to synchronize the detection unit 113 and the second clock generation unit. 114 and output to the data reproduction unit 133. On the other hand, when the connection state detection unit 134 determines that the two-wire cable is a positive connection, the reception data inversion unit 112 directly uses the downlink signal output from the reception driver 111 as the synchronization detection unit 113 and the second clock generation unit. 114 and output to the data reproduction unit 133.

  The synchronization detection unit 113 uses the first frequency clock (CLK) output from the first clock generation unit 131 and uses the preamble data included in the downlink signal output from the reception driver 111 to Synchronization (start timing of each bit of received data) is detected. Then, the synchronization detection unit 113 outputs a trigger signal serving as a reference for starting clock output to the second clock generation unit 114 at the timing when the unique pattern of the preamble data is detected, and an enable signal (SSCS) that permits the data reproduction operation Is output to the data reproducing unit 133. The details of the configuration of the synchronization detection unit 113 will be described later.

  The second clock generation unit 114 corresponds to the bit rate of the received data with reference to the first frequency clock (CLK) output from the first clock generation unit 131 at the timing instructed by the synchronization detection unit 113. A clock (SSCK) having two frequencies (for example, 4.8 MHz) is generated and output to the data reproducing unit 133.

<Configuration of doorphone master unit>
Next, the configuration of door phone master device 200 will be described using the block diagram of FIG. As shown in FIG. 4, door phone master device 200 includes a cable connection unit 201, a key input unit 202, a speaker 203, a microphone 204, an audio I / F unit 205, a display unit 206, and a control unit 207. The control unit 207 includes a first clock generation unit 231, a packet generation unit 232, a data reproduction unit 233, and a connection state detection unit 234 inside. The intercom base unit 200 also includes a transmission data processing unit 208, a transmission data inversion unit 209, a transmission driver 210, a reception driver 211, a routing control unit 212, a synchronization detection unit 213, and a second clock generation unit 214. The doorphone parent device 200 has N (N is a natural number) the cable connection unit 201, the transmission driver 210, and the reception driver 211.

  The cable connection portion 201-i (i is any integer from 1 to N) includes a connection terminal for a two-wire cable, one end on the indoor side of the two-wire cable, a transmission driver 210-i, and a reception driver 211. -I is connected in a state where signals can be transmitted. In addition, the other end of each two-wire cable is connected to the main unit of the entrance cordless handset 100, the extension monitor 300, or another door phone system. In FIG. 4, the case where the cable connection part 201-1 is connected to the main | base station of another door phone system is illustrated.

  The key input unit 202 includes a response button. When the response button is operated, the key input unit 202 outputs a signal indicating that to the control unit 207.

  The speaker 203 converts the analog audio data output from the audio I / F unit 205 into audio and outputs the audio.

  The microphone 204 collects surrounding sounds, converts them into analog sound data, and outputs the analog sound data to the sound I / F unit 205.

  The audio I / F unit 205 converts the digital audio data output from the control unit 207 into analog audio data, adjusts the signal level, and outputs the analog audio data to the speaker 203. The audio I / F unit 205 adjusts the signal level of the analog audio data output from the microphone 204, converts the analog audio data into digital audio data, and outputs the digital audio data to the control unit 207. Such analog / digital conversion is performed by an A / D, D / A converter (not shown).

  The audio I / F unit 205 outputs data obtained by performing predetermined audio compression processing on the data obtained by digitally converting the analog audio data output from the microphone 204 to the control unit 207 as digital audio data. May be. In addition, when the digital audio data output from the control unit 207 is data obtained by performing predetermined audio compression processing, the audio I / F unit 205 performs predetermined audio expansion processing on the data. To digital / analog conversion.

  The display unit 206 includes a liquid crystal display, reproduces digital video data output from the control unit 207, and displays an entrance video. When the digital video data output from the control unit 207 is data obtained by performing a predetermined moving image compression process, a predetermined moving image expansion process is performed on the data to display a video.

  The control unit 207 controls each unit of the door phone master device 200. In addition, the control unit 207 sends a transmission control section (SW CON) that indicates a transmission section that permits transmission and a reception section that permits reception to each transmission driver 210-i, each reception driver 211-i, and a routing control section. It outputs to 212.

  The first clock generation unit 231 of the control unit 207 is a clock for sampling received data, and is based on crystal oscillation and has a first frequency corresponding to n times the bit rate of the received data (for example, 48 MHz (n = 10)) clock (CLK) is generated and output to the synchronization detector 213 and the second clock generator 214.

  The packet generation unit 232 of the control unit 207 generates a downlink packet for realizing a call with video. Specifically, the packet generation unit 232 appropriately divides the digital audio data output from the audio I / F unit 205 and writes it in the user data field of each slot, and writes the control data in the control data field of each slot. Further, the packet generation unit 232 writes the preamble data and the sync pattern in each slot, and generates a downlink packet (transmission data). Furthermore, the packet generation unit 232 generates a transmission enable signal (SSCS) and a transmission second frequency (for example, 4.8 MHz) clock (SSCK). Then, the packet generation unit 232 outputs the downlink packet to the transmission data processing unit 208 in synchronization with the transmission enable signal (SSCS) and the clock (SSCK).

  In addition, the packet generation unit 232 may output control data related to the operation of the doorphone master device 200 or the operation of the front door device 100 to the transmission data processing unit 208 as data to be transmitted to the front door device 100. . Such control data includes, for example, the camera operation (data rate, pan, tilt, light, shutter, filter, etc.) of the doorphone master unit 200 to the entrance slave unit 100 and various sensors provided in the entrance slave unit 100. A control signal for controlling the operation of the device from door phone parent device 200 is included. The control data includes a control signal for controlling the operation of a device (such as a gate electronic key) arranged outdoors via a wireless communication circuit or the like (not shown) provided in the entrance cordless handset 100. Is included.

  When the data reproduction unit 233 of the control unit 207 receives the enable signal (SSCS) from the synchronization detection unit 213, the data reproduction unit 233 uses the second frequency clock (SSCK) output from the second clock generation unit 214, and the routing control unit 212. The upstream signal output from is demodulated to obtain the upstream packet. Then, the data reproducing unit 233 outputs the digital audio data included in the upstream packet to the audio I / F unit 205, outputs the digital video data included in the upstream packet to the display unit 206, and the sync pattern included in the upstream packet. Is output to the connection state detection unit 234.

  The connection state detection unit 234 of the control unit 207 stores the normal connection check sync pattern and the reverse connection check sync pattern, and converts the received data sync pattern output from the data reproduction unit 233 into the normal connection check sync pattern and Match with reverse connection check sync pattern. The connection state detection unit 234 determines that the two-wire cable is correctly connected when the received data sync pattern and the normal connection check sync pattern completely match, and the received data sync pattern and the reverse connection check sync pattern are determined. If the two completely match, it is determined that the two-wire cable is reversely connected. Then, the connection state detection unit 234 outputs an inversion control signal (INV CON) indicating the determination result to the transmission data inversion unit 209.

  When the transmission data processing unit 208 receives the enable signal (SSCS) from the packet generation unit 232, the transmission data processing unit 208 uses the second frequency clock (SSCK) output from the packet generation unit 232, and the downlink data output from the packet generation unit 232. Modulation processing is performed on the packet data to generate a downlink signal, which is output to the routing control unit 212.

  When the connection state detection unit 234 determines that the two-wire cable is reversely connected, the transmission data inverting unit 209 inverts the downlink signal output from the routing control unit 212 and outputs the inverted signal to the transmission driver 210-1. On the other hand, when the connection state detection unit 234 determines that the two-wire cable is a normal connection, the transmission data inversion unit 209 outputs the downlink signal output from the routing control unit 212 to the transmission driver 210-1 as it is.

  The transmission driver 210-1 transmits a downlink signal to the master unit of another door phone system via the cable connection unit 201-1 in the transmission section instructed by the switching control signal (SW CON) from the control unit 207. . The transmission driver 210-i (in this case, i is other than 1) transmits the downstream signal to the entrance via the cable connection unit 201-i in the transmission section instructed by the switching control signal (SW CON) from the control unit 207. It transmits to the subunit | mobile_unit 100 or the expansion monitor 300. FIG.

  The reception driver 211-i receives an upstream signal transmitted from the front cordless handset 100, the extension monitor 300, or the parent device of another door phone system via the cable connection unit 201-i. Then, the reception driver 211-i outputs an uplink signal to the routing control unit 212 in the reception period instructed by the switching control signal (SW CON) from the control unit 207.

  The routing control unit 212 transmits the uplink signal transmitted from the front door slave unit 100 and output from the reception driver 211-i to the master unit 200. When the destination signal is addressed to the master unit 200, the synchronization detection unit 213, the second clock generation unit 214, the data reproduction If it is addressed to the expansion monitor 300, it is output to the corresponding transmission driver 210-i. In addition, the routing control unit 212 outputs the downlink signal output from the transmission data processing unit 208 and addressed to the entrance slave device 100 to the corresponding transmission driver 210-i. In addition, the routing control unit 212 outputs the uplink signal addressed to the entrance slave device 100 transmitted from the extension monitor 300 and output from the reception driver 211-i to the corresponding transmission driver 210-i.

  The synchronization detection unit 213 uses the first frequency clock (CLK) output from the first clock generation unit 231 and uses the preamble data included in the uplink signal output from the routing control unit 212, to the entrance terminal 100. (The timing at the beginning of each bit of received data) is detected. Then, the synchronization detection unit 213 outputs a trigger signal serving as a reference for starting clock output to the second clock generation unit 214 at the timing when the unique pattern of the preamble data is detected, and an enable signal (SSCS) that permits the data reproduction operation Is output to the data reproducing unit 233.

  The second clock generation unit 214 corresponds to the bit rate of the received data based on the first frequency clock (CLK) output from the first clock generation unit 231 at the timing instructed by the synchronization detection unit 213. A clock (SSCK) having two frequencies (for example, 4.8 MHz) is generated, and a clock having the second frequency is output to the data reproducing unit 233.

<Configuration of additional monitor>
Next, the configuration of the extension monitor 300 will be described with reference to the block diagram of FIG. As illustrated in FIG. 5, the extension monitor 300 includes a cable connection unit 301, a key input unit 302, a speaker 303, a microphone 304, an audio I / F (interface) unit 305, a display unit 306, and a control unit 307. The control unit 307 includes a first clock generation unit 331, a packet generation unit 332, a data reproduction unit 333, and a connection state detection unit 334 inside. The expansion monitor 300 includes a transmission data processing unit 308, a transmission data inversion unit 309, a transmission driver 310, a reception driver 311, a reception data inversion unit 312, a synchronization detection unit 313, and a second clock generation unit 314.

  The cable connection unit 301 includes a connection terminal for a two-wire cable, and connects the one end on the additional monitor side of the two-wire cable to the reception driver 311 and the transmission driver 310 in a state where signals can be transmitted. Note that the other end of the two-wire cable is connected to the doorphone master unit 200.

  The key input unit 302 includes a call button. When the call button is operated, the key input unit 302 outputs a signal indicating that to the control unit 307.

  The speaker 303 converts analog audio data output from the audio I / F unit 305 into audio and outputs the audio.

  The microphone 304 collects ambient sound, converts it into analog sound data, and outputs it to the sound I / F unit 305.

  The audio I / F unit 305 converts the digital audio data output from the control unit 307 into analog audio data, adjusts the signal level, and outputs the analog audio data to the speaker 303. The audio I / F unit 305 adjusts the signal level of the analog audio data output from the microphone 304, converts the analog audio data into digital audio data, and outputs the digital audio data to the control unit 307. Such analog / digital conversion is performed by an A / D, D / A converter (not shown).

  Note that the audio I / F unit 305 outputs data obtained by performing predetermined audio compression processing on the data obtained by digitally converting the analog audio data output from the microphone 304 to the control unit 307 as digital audio data. May be. In addition, when the digital audio data output from the control unit 307 is data obtained by performing predetermined audio compression processing, the audio I / F unit 305 performs predetermined audio expansion processing on the data. To digital / analog conversion.

  The display unit 306 includes a liquid crystal display, reproduces the digital video data output from the control unit 307, and displays the entrance video. When the digital video data output from the control unit 307 is data obtained by performing a predetermined moving image compression process, the predetermined video expansion process is performed on the data to display a video.

  The control unit 307 controls each unit of the extension monitor 300. In addition, the control unit 307 outputs to the transmission driver 310 and the reception driver 311 a switching control signal (SW CON) instructing a transmission period that permits transmission and a reception period that permits reception.

  The first clock generation unit 331 of the control unit 307 is a clock for sampling received data, and is based on crystal oscillation and has a first frequency (for example, 48 MHz (n = 10)) clock (CLK) is generated and output to the synchronization detector 313 and the second clock generator 314.

  The packet generation unit 332 of the control unit 307 generates an uplink packet for realizing a call with video. Specifically, the packet generation unit 332 appropriately divides the digital audio data output from the audio I / F unit 305, writes it in the user data field of each slot, and writes the control data in the control data field of each slot. Further, the packet generation unit 332 writes preamble data and a sync pattern in each slot, and generates an uplink packet (transmission data). Further, the packet generation unit 332 generates a transmission enable signal (SSCS) and a transmission second frequency (for example, 4.8 MHz) clock (SSCK). Then, the packet generation unit 332 outputs the uplink packet to the transmission data processing unit 308 in synchronization with the transmission enable signal (SSCS) and the clock (SSCK).

  When the data reproduction unit 333 of the control unit 307 receives the enable signal (SSCS) from the synchronization detection unit 313, the data reproduction unit 333 uses the second frequency clock (SSCK) output from the second clock generation unit 314, and receives the data inversion unit. The downlink signal output from 312 is demodulated to obtain a downlink packet. Then, the data reproducing unit 333 outputs the digital video data included in the downlink packet to the display unit 306, outputs the digital audio data included in the downlink packet to the audio I / F unit 305, and the sync pattern included in the downlink packet. Is output to the connection state detection unit 334.

  The connection state detection unit 334 of the control unit 307 stores the normal connection check sync pattern and the reverse connection check sync pattern, and converts the received data sync pattern output from the data reproduction unit 333 into the normal connection check sync pattern and Match with reverse connection check sync pattern. The connection state detection unit 334 determines that the two-wire cable is correctly connected when the sync pattern of the received data completely matches the sync pattern for the normal connection check, and the sync pattern of the received data and the sync pattern for the reverse connection check If the two completely match, it is determined that the two-wire cable is reversely connected. Then, the connection state detection unit 334 outputs an inversion control signal (INV CON) indicating the determination result to the transmission data inversion unit 309 and the reception data inversion unit 312.

  When the transmission data processing unit 308 receives the enable signal (SSCS) from the packet generation unit 332, the transmission data processing unit 308 uses the second frequency clock (SSCK) output from the packet generation unit 332, and the uplink data output from the packet generation unit 332. Modulation processing is performed on the packet data to generate an uplink signal, which is output to the transmission data inverting unit 309.

  When the connection state detection unit 334 determines that the two-wire cable is reversely connected, the transmission data inversion unit 309 inverts the uplink signal output from the transmission data processing unit 308 and outputs the inverted signal to the transmission driver 310. On the other hand, the transmission data inverting unit 309 outputs the uplink signal output from the transmission data processing unit 308 to the transmission driver 310 as it is when the connection state detection unit 334 determines that the two-wire cable is a normal connection.

  The transmission driver 310 transmits an upstream signal to the intercom base unit 200 via the cable connection unit 301 in the transmission section instructed by the switching control signal (SW CON) from the control unit 307.

  The reception driver 311 receives the downlink signal transmitted from the doorphone master device 200 via the cable connection unit 301. Then, the reception driver 311 outputs the downlink signal to the reception data inversion unit 312 in the reception period instructed by the switching control signal (SW CON) from the control unit 307.

  When the connection state detection unit 334 determines that the two-wire cable is reversely connected, the reception data inversion unit 312 inverts the downlink signal output from the reception driver 311 so as to invert the synchronization detection unit 313 and the second clock generation unit. 314, and output to the data reproduction unit 333. On the other hand, when the connection state detection unit 334 determines that the two-wire cable is a positive connection, the reception data inversion unit 312 directly uses the downlink signal output from the reception driver 311 as the synchronization detection unit 313 and the second clock generation unit. 314, and output to the data reproduction unit 333.

  The synchronization detection unit 313 uses the first frequency clock (CLK) output from the first clock generation unit 331 and uses the preamble data included in the downlink signal output from the reception driver 311 to Synchronization (start timing of each bit of received data) is detected. Then, the synchronization detection unit 313 outputs a trigger signal serving as a reference for starting clock output to the second clock generation unit 314 at the timing when the unique pattern of the preamble data is detected, and an enable signal (SSCS) that permits the data reproduction operation Is output to the data reproduction unit 333.

  The second clock generation unit 314 corresponds to the bit rate of the received data based on the first frequency clock (CLK) output from the first clock generation unit 331 at the timing instructed by the synchronization detection unit 313. A clock (SSCK) having two frequencies (for example, 4.8 MHz) is generated and output to the data reproducing unit 333.

  Although not shown in the figure, the front door device 100, the doorphone master device 200, and the extension monitor 300 are, for example, a CPU (Central Processing Unit), a storage medium such as a ROM (Read Only Memory) storing a control program, a RAM (Random Access And a communication circuit. In this case, the function of each unit described above is realized by the CPU executing the control program.

<Example of modulation processing>
Next, an example of modulation processing performed by the transmission data processing unit 108 (208, 308) will be described with reference to FIGS. 6 and 7 show a case where the Manchester code is employed.

  The transmission data processing unit 108 (208, 308) generates one signal corresponding to each data (1 bit) of the packet for each cycle Tm. When the Manchester code is employed, the transmission data processing unit 108 (208, 308) generates a modulation signal 402 by causing the data 401 having the value “0” to rise from Low to High as shown in FIG. . Also, the transmission data processing unit 108 (208, 308) causes the data 411 having the value “1” to fall from High to Low, and generates a modulated signal 412.

  Then, as shown in FIG. 7, for the data string 421 of “0, 0, 1,..., 1, 0”, the transmission data processing unit 108 (208, 308) corresponds to the value of each bit. Thus, a modulation signal 422 having a rising edge or a falling edge is generated every period Tm.

<Example of preamble data>
Next, an example of preamble data used in the present embodiment will be described with reference to FIG.

  As shown in FIG. 8, the preamble data (4 bytes = 32 bits) used in the present embodiment has a pattern of “0” from the first byte to the third byte, and the fourth byte is “0” from the beginning. ", The last 1 bit is a pattern of" 1 ". As a result, the preamble data shown in FIG. 8 has a unique pattern in which the H (High) period is longer than the others in the 7th and 8th bits (the 31st and 32nd bits from the beginning) of the 4th byte.

  When the two-wire cable is reversely connected, if the inversion processing is not performed in the transmission side device, the preamble data is L (Low) in the 7th and 8th bit portions of the 4th byte when received by the reception side device. This is a unique pattern with a longer period than others.

<Internal configuration of synchronization detector>
Next, the details of the internal configuration of the synchronization detection unit 113 of the front door device 100 will be described with reference to FIG. In the description, FIG. 10 is used in conjunction with FIG. 9 in order to facilitate understanding of the synchronization detection processing of the present embodiment. In the example of FIG. 10, the preamble data and its unique pattern are those shown in FIG.

  As illustrated in FIG. 9, the synchronization detection unit 113 includes a first unique pattern detection unit 151, a second unique pattern detection unit 152, and an enable signal generation unit 153.

  The first unique pattern detection unit 151 stores a check unique pattern (hereinafter referred to as “positive connection check unique pattern” (in the example of FIG. 9, [HHHLLLLLLL])) when the two-wire cable is positively connected. ing. Then, the first unique pattern detection unit 151 samples the preamble data included in the reception data output from the reception data output from the reception data inversion unit 112 with the clock of the first clock generation unit 131, and performs a positive connection. The sampling value corresponding to the number of check unique patterns is collated with the unique pattern for positive connection check. The first unique pattern detection unit 151 determines that the unique pattern has been detected when the sampling value and the unique pattern for the positive connection check completely match, and outputs a signal indicating that to the enable signal generation unit 153. In the example of FIG. 10, ten sampling values in the sample section 501 completely match the unique pattern for positive connection check. FIG. 10 shows a case where the first clock generation unit 131 generates a 48 MHz clock (CLK) and the second clock generation unit 114 generates a 4.8 MHz clock (SSCK).

  The second unique pattern detection unit 152 is a reverse pattern of the unique pattern for normal connection check, and a unique pattern for check when the two-wire cable is reversely connected (hereinafter referred to as “reverse connection check unique pattern”). ([LLLHHHHHHH] in the example of FIG. 9)) is stored. The second unique pattern detection unit 152 samples the preamble data included in the reception data output from the reception data inversion unit 112 at the same timing as the first unique pattern detection unit 151, and reversely connects the sampling value. Check unique patterns for checking. The second unique pattern detection unit 152 determines that the unique pattern has been detected when the sampling value and the reverse connection check unique pattern completely match, and indicates a signal indicating this (in the example of FIG. 10, the SSCS L (Low) signal) is output to the enable signal generation unit 153.

  When the enable signal generation unit 153 receives a signal indicating that a unique pattern has been detected from either the first unique pattern detection unit 151 or the second unique pattern detection unit 152, the trigger that becomes a reference for starting clock output The signal is output to the second clock generation unit 114, and an enable signal for permitting the data recovery operation is output to the data recovery unit 133 of the control unit 107.

  In this case, the second clock generation unit 114 has a first frequency clock (t0 in FIG. 10) after a predetermined number of clocks (section 502 in FIG. 10) from the timing when the trigger signal is input from the enable signal generation unit 153. Is used as a start timing to generate a clock. In the example of FIG. 10, since SSCK is a clock obtained by dividing CLK by 10, the prescribed number of clocks is “10”.

  The internal configurations of the synchronization detection unit 213 of the doorphone master unit 200 and the synchronization detection unit 313 of the extension monitor 300 are also the same as the internal configuration of the synchronization detection unit 113 of the front door device 100 shown in FIG.

<Flow of synchronization detection processing>
Next, the flow of the synchronization detection process in the entrance cordless handset 100 (synchronization detection unit 113, connection state detection unit 134) will be described with reference to FIG.

  In step S <b> 610, the synchronization detection unit 113 uses the first unique pattern detection unit 151 and the second unique pattern detection unit 152 to output the downlink before demodulation output from the reception driver 111 using the clock of the first clock generation unit 131. The preamble data included in the signal is sampled, and the unique pattern of the preamble data is checked.

  If the unique pattern can be detected (S620: YES), the flow proceeds to step S630 on the assumption that the bit synchronization can be established. If not detected (S620: NO), the flow returns to step S610 to return to the unique pattern. Check again.

  In step S630, the connection state detection unit 134 checks the sync pattern of the reception data output from the data reproduction unit 133.

  If the sync pattern of the received data matches the sync pattern for normal connection check (S640: YES), in step S650, the connection state detection unit 134 determines that the two-wire cable is a normal connection, and performs synchronization detection processing. finish.

  When the sync pattern of the received data matches the sync pattern for reverse connection check (S640: NO, S660: YES), in step S670, the connection state detection unit 134 determines that the two-wire cable is reverse connected. Then, the synchronization detection process ends.

  If the sync pattern of the received data does not match either the reverse connection check sync pattern or the reverse connection check sync pattern (S640: NO, S660: NO), the connection state detection unit 134 in step S680. Determines that the sync pattern detection has failed, returns the flow to step S610, and checks the unique pattern again.

<Operation of each device>
Next, the operation of each device will be described.

<Operation of entrance cordless handset>
FIG. 12 is a flowchart illustrating an example of the operation of the front door device 100.

  In step S1010, the control unit 107 determines whether the call button has been operated. When the call button is operated (S1010: YES), the control unit 107 advances the flow to step S1020, and when not operated (S1010: NO), advances the flow to step S1100 described later.

  In step S <b> 1020, control unit 107 transmits a calling signal to door phone parent device 200.

  In step S1030, control unit 107 determines whether a response signal has been received from intercom master device 200 or not. When the response signal is not received (S1030: NO), the control unit 107 returns the flow to step S1020, and when the response signal is received (S1030: YES), the control unit 107 advances the flow to step S1040. Note that if the control unit 107 does not receive a response signal even if the call signal is transmitted a predetermined number of times, the control unit 107 may advance the flow to step S1100 described later.

  In step S <b> 1040, the control unit 107 starts audio input and video shooting using the microphone 104, the audio I / F unit 105, and the camera unit 106. In addition, the control unit 107 uses the packet generation unit 132 and the transmission data processing unit 108 to start packetizing and encoding various data (control data / digital audio data / digital video data) to be transmitted. Note that the control unit 107 may perform transmission rate control of digital audio data and digital video data.

  In step S1050, control unit 107 determines whether or not it is a slave unit side transmission section. If it is a transmission interval (S1050: YES), the control unit 107 advances the flow to step S1060. If not (S1050: NO), the control unit 107 advances the flow to step S1070 described later.

  In step S <b> 1060, control unit 107 uses transmission driver 110 to transmit the upstream signal generated by encoding to door phone parent device 200 via a two-wire cable. In addition, the control part 107 stops transmission of an uplink signal when a transmission area is complete | finished.

  In step S1070, control unit 107 determines whether or not it is a parent device side transmission section. When it is a transmission section (S1070: YES), the control unit 107 advances the flow to step S1080. When it is not a transmission section (S1070: NO), the control section 107 advances the flow to step S1090 described later.

  In step S1080, the control unit 107 starts receiving a downlink signal, extracting various data (control data / audio data), and outputting audio. Note that the control unit 107 stops receiving a downlink signal or extracting various data when the transmission period ends.

  In step S <b> 1090, control unit 107 determines whether or not the call between entrance slave device 100 and doorphone master device 200 has ended. For example, the control unit 107 determines that the call has ended when it receives a signal indicating that a call end operation has been performed on the doorphone base unit 200 from the doorphone base unit 200. If the call has not ended (S1090: NO), control unit 107 returns the flow to step S1050. If the call has ended (S1090: YES), control proceeds to step S1100.

  In step S1100, control unit 107 determines whether or not an instruction to end processing related to the door phone function has been given. For example, when the control unit 107 receives a signal indicating that the operation of stopping the door phone function has been performed on the doorphone master unit 200 from the doorphone master unit 200, the control unit 107 determines that the end of the process has been instructed. If the end of the process is not instructed (S1100: NO), the control unit 107 returns the flow to step S1010, and if instructed to end the process (S1100: YES), ends the series of processes.

<Operation of doorphone master unit>
FIG. 13 is a flowchart showing an example of the operation of the doorphone parent device 200.

  In step S2010, the control unit 207 determines whether a call signal has been received from the front door device 100. When the call signal is received (S2010: YES), the control unit 207 advances the flow to step S2020. When the call signal is not received (S2010: NO), the control unit 207 advances the flow to step S2090 described later.

  In step S2020, the control unit 207 transmits a response signal to the front door device 100 and outputs a ringing tone using the voice I / F unit 205 and the speaker 203.

  In step S2030, the control unit 207 starts voice input using the microphone 204 and the voice I / F unit 205. In addition, the control unit 207 uses the packet generation unit 232 and the transmission data processing unit 208 to start packetizing and encoding various data (control data / digital audio data) to be transmitted. Note that the control unit 207 may perform digital audio data transmission rate control.

  In step S2040, control unit 207 determines whether or not it is a slave unit side transmission section. The control unit 207 advances the flow to step S2050 if it is a transmission interval (S2040: YES), and advances the flow to step S2060 described later if it is not a transmission interval (S2040: NO).

  In step S2050, the control unit 207 starts receiving an upstream signal and extracting various data (control data / audio data / video data). In addition, the control unit 207 uses the audio I / F unit 205, the speaker 203, and the liquid crystal display to start outputting audio and video. Note that the control unit 207 stops receiving the uplink signal or extracting various data when the transmission period ends.

  In step S2060, the control unit 207 determines whether or not it is a parent device side transmission section. When it is a transmission section (S2060: YES), the control unit 207 advances the flow to step S2070. When it is not a transmission section (S2060: NO), the control section 207 advances the flow to step S2080 described later.

  In step S2070, the control unit 207 uses the transmission driver 210 to transmit the downlink signal generated by encoding to the front door device 100 via the two-wire cable. However, it is desirable that the control unit 207 does not transmit digital audio data until the response button is operated as described above. Note that the control unit 207 stops the transmission of the downlink signal when the transmission period ends.

  In step S2080, control unit 207 determines whether or not the telephone conversation between entrance slave device 100 and doorphone master device 200 has ended. For example, the control unit 207 determines that the call is ended when it is detected that an operation for ending the call is performed on the intercom base unit 200. In addition, it is desirable that the control unit 207 transmits a signal indicating that to the entrance terminal 100 when an operation for terminating the call is performed. If the call has not ended (S2080: NO), control returns to step S2040. If the call has ended (S2080: YES), control proceeds to step S2090.

  In step S2090, control unit 207 determines whether an instruction to end the process related to the door phone function has been given. For example, when the control unit 207 detects that the doorphone function stop operation has been performed on the doorphone master unit 200, the control unit 207 determines that the end of the process has been instructed. In addition, when the operation of stopping the door phone function is performed, the control unit 207 desirably transmits a signal indicating that to the front door device 100. If the control unit 207 is not instructed to end the process (S2090: NO), the control unit 207 returns the flow to step S2010, and if instructed to end the process (S2090: YES), ends the series of processes.

<Effects of the present embodiment>
As described above, according to the present embodiment, when the two-wire cable is reversely connected, the transmission / reception is performed after inverting the data in either the transmission-side device or the reception-side device. The receiving apparatus can demodulate data regardless of the connection state of the wire cable. Therefore, the construction worker can wire the two-wire cable without worrying about the connection state (normal connection or reverse connection), so that the work efficiency at the time of wiring the two-wire cable can be increased.

  The present disclosure is suitable for use in a door phone system including an entrance child device with a camera and a door phone parent device.

DESCRIPTION OF SYMBOLS 1 Door phone system 100 Entrance unit 101, 201, 301 Cable connection part 102, 202, 302 Key input part 103, 203, 303 Speaker 104, 204, 304 Microphone 105, 205, 305 Audio | voice I / F part 106 Camera part 107, 207, 307 Control unit 108, 208, 308 Transmission data processing unit 109, 209, 309 Transmission data inversion unit 110, 210, 310 Transmission driver 111, 211, 311 Reception driver 112, 312 Reception data inversion unit 113, 213, 313 Synchronization Detection unit 114, 214, 314 Second clock generation unit 131, 231, 331 First clock generation unit 132, 232, 332 Packet generation unit 133, 233, 333 Data reproduction unit 134, 234, 334 Connection state detection unit 151 First of Martinique pattern detecting section 152 second unique pattern detection unit 153 an enable signal generating unit 200 indoor apparatus 206, 306 display unit 212 routing control unit 300 Expansion Monitor

The present disclosure relates to the intercom system you and the communication method.

The purpose of the present disclosure is to provide an intercom system AND ITS communication method construction worker can be improved working efficiency during two-wire cabling.

Intercom system of the present disclosure, the master unit is connected via a handset and two-wire cable, wherein a door phone system to transmit and receive packet signals by time-division duplex between the master unit and the slave unit, The slave unit has a camera, a microphone, and a speaker, transmits an upstream packet signal including video data obtained by the camera and audio data obtained by the microphone to the master unit, and receives a downlink packet from the master unit Receiving the signal and reproducing the data, outputting the audio data included in the downlink packet signal from the speaker, the master unit has a display unit, a microphone and a speaker, and the uplink packet signal from the slave unit Receiving and reproducing the data, displaying the video data included in the uplink packet signal on the display unit and the audio data included in the uplink packet signal. Output from the over mosquito, and sends the downlink packet signals comprising voice data obtained by the microphone to the handset, or slave machine, the two-wire cable is a reverse connection or a positive connection judgment, if the two-wire cable is a reverse connection, performs a reproduction of data from the inverting the downstream packet signal received, and transmits after inverting the upstream packet signal, the master unit, Even if the two-wire cable is reversely connected, data is reproduced without inverting the upstream packet signal and transmitted without inverting the downstream packet signal .

The communication method present disclosure, a time display unit, the master unit having a microphone and speaker, a camera, are connected via a handset and two-wire cable having a microphone and a speaker, between the master unit and the slave unit A communication method of a door phone system that transmits and receives a packet signal by division duplex, wherein the slave unit determines whether the two-wire cable is a normal connection or a reverse connection, and video data obtained by the camera and The upstream packet signal including the voice data obtained by the microphone is transmitted to the master unit without being inverted when the two-wire cable is connected in the normal direction, and inverted when the two-wire cable is connected in the reverse direction. transmitted from to the master unit, the master unit, to reproduce the data by receiving the upstream packet signal from the slave unit, when displaying the image data included in the uplink packet signal by the display unit bets Audio data included in the uplink packet signal is output from the speaker, and a downlink packet signal including the audio data obtained by the microphone is transmitted to the slave unit. The slave unit transmits the downlink packet signal from the master unit. When the two-wire cable is a normal connection, data is reproduced without inverting the downlink packet signal. When the two-wire cable is reversely connected, the downlink packet signal is inverted. After that, the data is reproduced, and the audio data included in the downlink packet signal is output from the speaker .

Claims (8)

The slave unit of the door phone system in which a master unit and a slave unit are connected via a two-wire cable, and transmits and receives packet signals by time division duplex between the master unit and the slave unit,
A connection state detection unit for determining whether the two-wire cable is a normal connection or a reverse connection;
When the two-wire cable is reversely connected, a reception unit that performs reception processing after inverting the received data from the master unit;
When the two-wire cable is reversely connected, a transmission unit that performs transmission processing after inverting the transmission data to the base unit;
A handset comprising The connection state detection unit
Storing a first sync pattern that is known when the two-wire cable is positively connected, and a second sync pattern obtained by inverting the first sync pattern;
When the sync pattern detected from the received data matches the first sync pattern, it is determined that the two-wire cable is a positive connection, and the detected sync pattern matches the second sync pattern Determining that the two-wire cable is reversely connected,
The subunit | mobile_unit of Claim 1. The master unit of the door phone system in which a master unit and a slave unit are connected via a two-wire cable, and transmits and receives packet signals by time division duplex between the master unit and the slave unit,
A connection state detection unit for determining whether the two-wire cable is a normal connection or a reverse connection;
A receiving unit that performs reception processing on the received data from the master unit of another door phone system;
When the two-wire cable is reversely connected, a transmission unit that performs transmission processing after inverting the transmission data to the master unit of the other door phone system;
A master unit equipped with The master unit of the door phone system in which a master unit and a slave unit are connected via a two-wire cable, and transmits and receives packet signals by time division duplex between the master unit and the slave unit,
A connection state detection unit for determining whether the two-wire cable is a normal connection or a reverse connection;
When the two-wire cable is reversely connected, a reception unit that performs reception processing after inverting the received data from the master unit of another door phone system;
A transmission unit that performs transmission processing on the transmission data to the master unit of another door phone system,
A master unit equipped with The connection state detection unit
Storing a first sync pattern that is known when the two-wire cable is positively connected, and a second sync pattern obtained by inverting the first sync pattern;
When the sync pattern detected from the received data matches the first sync pattern, it is determined that the two-wire cable is a positive connection, and the detected sync pattern matches the second sync pattern Determining that the two-wire cable is reversely connected,
The master unit according to claim 3 or 4. A monitor that is added to a door phone system composed of a parent device and a child device, is connected to the parent device via a two-wire cable, and transmits and receives packet signals by time division duplex with the parent device,
A connection state detection unit for determining whether the two-wire cable is a normal connection or a reverse connection;
When the two-wire cable is reversely connected, a reception unit that performs reception processing after inverting the received data from the master unit;
When the two-wire cable is reversely connected, a transmission unit that performs transmission processing after inverting the transmission data to the base unit;
A monitor comprising: The connection state detection unit
Storing a first sync pattern that is known when the two-wire cable is positively connected, and a second sync pattern obtained by inverting the first sync pattern;
When the sync pattern detected from the received data matches the first sync pattern, it is determined that the two-wire cable is a positive connection, and the detected sync pattern matches the second sync pattern Determining that the two-wire cable is reversely connected,
The monitor according to claim 6. A communication method of a door phone system in which a parent device and a child device are connected via a two-wire cable, and packet signals are transmitted and received between the parent device and the child device by time division duplex,
The slave is
Determining whether the two-wire cable is a normal connection or a reverse connection;
When the two-wire cable is reversely connected, a step of performing a reception process after inverting the received data from the master unit;
When the two-wire cable is reversely connected, the transmission process to the master unit is reversed, and then the transmission process is performed.
The base unit is
Transmitting data to the slave unit via the two-wire cable;
Receiving data from the slave unit via the two-wire cable,
Communication method.

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