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Wireless building intercom system
2012-02-07 10:01:08

Wireless building intercom system

Current Situation


It is relatively simple for the the early building intercom products, which, being used in the single house or unit, just allows basic visiting function. The competitive manufacturers have concentrated developing the web-shaped, intelligent neighborhood since 2000. The integration level of the intelligent system is much higher, which can be exemplified by the realization of multiple outdoor devices and management system, then the integrated security alarming and the release of the service and information. Besides, there are other manufacturers who have integrated three monitors remote copy, monitoring and petrol system while the stability of the products remains to be improved.


Wire arrangement structure

Nowadays, the most common way is to set up multiple cords while the video is transferred by coaxial cable. RVV cable is usually used to transferred audio, data, but sometimes reticle, such as Xi'an Xiyuan, Shenzhen Shidean, Xiamen Lilin etc. There are also individual manufacturer applying two-wire signal modulation transmission and wireless products.

There are three problems that need solving: audio and video quality, data transmission quality and the two/three wire audio transmission in the wire structure of building intercom system. The three-wire transmission can better deal with the problem of signal amplification and modulation.

It usually use special decoding chips, CAN receiver and RS-485 etc to transfer data. It shows advantages in signal anti-interference for difference data transfer mode such a s CAN, RS-485 while the data being transferred by baseband level is easily interfered, whici is particularly obvious in the scaled small networks. In way of wire structure, most products are applied trunk method which divide the trunk(networks) and sub-trunk(unit), combined by the routers(USB hub).

There shapes a bottom to top leveled main wire system structure from the central computer, management computer, residential outdoor device, unit outdoor device, double confirmation device to indoor device of the current equipment. It is connected by the dis-concentrator, which can be designed to settle in the terminal equipment(like unit outdoor device). The alarming control is connected to the indoor device.

The above terminal equipment can be flexibly combined for different residential.


Developing trend


1. The building intercom system is the basic disposition for the intelligent neighborhood which is compulsory in the new building design in some cities.


2. Uniform standard for wire structure and product ports

There lacks compatibility for transmission method and ports manufactured by different factory, which is an obstacle for socializing of the engineering construction and after-sale service. Moreover, it is hard to maintain the system whose warranty expired. Concerned by related department, the standardization of wire structure and products port is irresistible.

3. Function diversity due to technology development

Image recognition in the outdoor device and fingerprint recognition are more humanized. Audio digitalization technology and ARM embedded Technology enables direct access to Broadband Network(BBN) and Bluetooth technology relieves building intercom system of wire structure. There has been launched by Xi'an Kaiyuan a digitalized family information machine based on the BBN which integrated building intercom, information access, security guarding and appliance control etc. It is a relatively advanced solution for the intelligent neighborhood system, which bases the platform on BBN, avoiding different wire structures.

4. Cost down, Market broaden

Nowadays, it stays high point for the costs generated in selling, engineering installation and service for the large-scale manufacturer. As the processing of standardization, the costs will be lowered down gradually.

In a word, the building intercom system is heading for the new developing stage but immature in many prospects. The future intercom product will highly develop.

2. Introduction for different kinds of system.

There can be classified as Pressing mode, digital mode, digitalized across house model, pressing and video intercom, digitalized video intercom and digitalized aross house video intercom etc.

1) The single house model is equipped with non-video intercom, remote unlocking, active monitoring and inner house phone (connected to local call), unit system by TV and main device of unit video intercom.

2) Unit model , unit video and non-video intercom consist of pressing and dial-up mode.
•  The capacity for the pressing mode is relatively small which can be classified as the 15,18,21 and 27 house type. It is mainly applied for the building under 10 lays, which characterizes by one-press and easy operation.
•   It is larger for the capacity of the dial-up intercom system, which is mainly the 256house type and be applied for the building over 10 floors. It is characterized by same style with calling and luxurious interface.
•  These two system are applied the mainline to structure the mainline, whose decoding types are respectively floor decoding and indoor device decoding. The indoor device is usually compatible with the one of single house, which can realize video or non-video intercom, remote unlocking and connect to the administrative center and etc.


• The Community networking is applied by region centralized management (multi-function)., which is not only equipped with the video an non-video talking, remote unlocking and etc, but also can receive the alarming signal and emergency call from the detective of the community and can actively call for every user or group to realize the broadcasting function.

The function expansion networking type system achieved the copy and dispatch of the three table (water, electricity, gas), IC card entrance guard system and other residential property management system. The classification is gradually developed from simple to complex, from scattering to a whole. It is a symbol of the modernize residential for networking system which can realize the highest form of video and non-video talking of the intercom system.


3. The composition for the building intercom system
• The visitor can talk to the visited user through the principal device while the user control the locking/unlocking inside the building. The principal of the community can receive the message instantly and send out to the security guard. The system not only guarantees the security of the high-level housing, but also does convenience to the user to avoid going up/downstair.

• The user terminal for the intelligent intercom system is a digitalized terminal, which provide the user with a friendly operating interface to realize video talking, remote unlocking, monitoring the state of the doorway, security setup, emergency call, receiving message, inquiring and sending message to and from the administrative center and appliance control and etc.


System equipment composition
• There is a management center equipped with the central control device( main control device) in every intelligent community while the large community can be divided into several districts. There is a certain control device for the each district which is called the sub-division control device. As for the conveniency of management and timely solution, there is an administrative office and control device for every building in some neighborhood. The control device is used for secure the communication between the administrative office and the user, unlocking for the visitors, record incidents, entrance guard authorization and property message solving and etc.
•  The device upon the entrance of the community is call outdoor device, by which the we can call all the users in the community and conduct bilateral talking.
•  The device placed on the unit entrance is called unit outdoor device, which can conduct calling the users or the central device.
•  If there are several entrance for the building, then there can be installed several unit outdoor principal devices. One is call principal device while the others are sub-unit as their functions are the same.
•  There can be entrance guard on the outdoor device, principal or sub-principal device, which can control the E-lock.
•  The device installed beside the door is called second confirmation device which can conduct bilateral talking and unlocking.

•  The intercom device which is installed in the user's house, is called extension.

They are the terminal equipment for public use.

There are some intermediate equipment which is indispensable for the intelligent building intercom system


1) Network switchboard: It should be equipped to every community, which is the network resource management. It should be connected to the switchboard for channel selection when talking, data communication mediation, interruption of signal and the protocol modification and etc.


2) Networking device: sub-management device(except building and whole control device), the principal device(excluding sub-principal), outdoor device should be allocated one networking device. It is the necessary equipment for networking, which can save wire cost and the trouble of wire structuring.

3) Decoder: it is the bridge for the extension and principal device which exemplifies three functions: a. Failure isolation. B. Enlarge the capacity of the extension. C. Elongate the distance between the extension and the principal device. There is obvious defect for those intercom system without decoder. As it is applied the mainline mode to connect the principal and extension device, once one failure occurs, the whole system will be out of function and the amount of extension device is limited.
4. System Working principle

The door is usually locked to avoid the unauthorized person to enter the building. The residents can be in and out of the building freely with the key. When there are visitors, the visitor should enter the room number of the visited user on the outdoor device to call the extension of the user. The visited person can conduct bilateral talking through the intercom device to recognize the identity of the visitors. After confirmation, the user apply the unlocking function of the intercom device to control the e-lock of the door to let the visitors in. The door will automatically close after the visitor came in. The security department of the residential can monitor the state of each intercom system through the management principal device. Once the door is open illegally or the intercom or circuit fail, the principal device will send out the alarming signal with the content and address. The administrative department can talk to the users mutually or the users can call each other. If the property management department can inform the user to summit the payment or the user inform the administrative department to repair the facility. Under emergency, the user can ask for help to the administrative department or other users etc.



It is called inner mainline for the wire between the principal and decoder. The cord numbers of the cable differs as the manufacturer varies. Like the HUiRUITONgG R2 system four-wire whose function are: two wire for audio, one for video intercom and the other for non-video intercom. The video intercom wire functions when the outdoor device or principal device(sub-principal device) call for the user. While the non-video intercom wire functions when the main control device, sub-control device or building control device calls for the user. As there are two intercom wire to realize two-way channel for intercom, which reduce the busy rate. The other two wires, one for GND and the other for data communication to unlock and alarm.

There are eight ports for a decoder with each one connected to the corresponding user.

The decoder is connected to the extension through a multiple cord wire (3~8 cord). The cord number is depended by the extension function while the average security intercom requires 3 cords. If the extension is attached to receiving the digital message, there should be one more cord to transfer the digital message DMA to improve the transmission rate.
The whole nerve center belongs to the network switchboard.

Example: calling the user from outdoor

Object: Illustrate a whole calling and speaking process.

When the visitor enter the address of the user and press confirm, the outdoor device would conduct communication conflict testing and send out communication request to the networks. When the switchboard receive the request, it would immediate send out approval to the outdoor device. Then the outdoor device would release the called user and its own name, the switchboard would inquire the principal of the user upon request. The principal device would check over the state of the visited extension and report to the switchboard immediately. The result will be reflected to outdoor device by the switchboard. Once the circuit and extension are free, the outdoor device will sound the ring tone and display the information of the visited user. At the same time, the indoor device will vibrate and ring to inform the user of the visiting. The user can conduct bilateral talking if he pick up the phone or press hand-free and unlocking the door.


Intelligent intercom extension

The final reflection of the intelligent intercom is the extension, whose function represent the intelligence degree.

There are the following characteristics except video intercom and unlocking.
• 1) Touch mode

There are two reason for applying the touch mode: Simple and pleasure appearance which is out of the restraint of keyboard. B. Intelligent product under the Chinese instruction which enable the one-touch operation.l


• 2)Wireless remote control

There are two kinds of remote control, namely RF remote control and infrared ray remote control and both show their advantages. RF control is applied the home use frequency (315M,433M) electromagnetic wave to transfer, which can transfer to long distance and penetrable. It is usually attached with the Specialized superheterodyne or superregenerative receiving mode, which is acute(-110db), stable and long-lived.

Infrared remote control, directional, could not penetrate the object and transfer within 5M, which is hard to interfered. There is remote control receiver in the extension which is convenient to on/off guard and can be used to emergency alarm and dis-alarm sometimes.


• 3) Intelligent card to withdraw guarding
There needs to enter the withdrawal code when required as routine, which is troublesome. In this regard, the user can withdraw easily with the intelligent card, which does favor to card integration.
• 4) Receiving Message

There is two ways for the extension to receive message, one is video message while the other is digital message. As the first one, when the user requires to review the message, the central computer will output the message in video signal, which takes up the intercom channel and is low confidentiality. As for the other one, the central computer sends message by way of data communication to the extension, which is fast and high confidentiality but not occupies the intercom channel.
• 5) Message Inquiry
•  The user can inquire the open related information, such as utilities bills, monthly installment, public notice etc.
• 6) Sending Message
•  The user can base their own requirements to text a message to the administrative office as to file up and solve.
• 7)Image storing
•  When there is calls for the host who is off, the extension will automatically store the visitor image for later review.
• 8) Message
•  Visitor can leave messages to extension when the host is off.
• 9) Appliance control platform
•  Operating through touching under the Chinese instruction to realize appliance control.

5. System design

System: outdoor host machine and extension, floor decoder, E-lock and specialized power supply.

Wire structure: Three main wire from host machine to floor decoder, two non polarized wire from decoder to extension.

Characteristics of wire: non-polarized user wire and two wire of the main wire so that the short-circuit of user wire would not impact the whole system.


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