User:U3573541/Public Address system with IP-based function

Background
A public address system (PA system) is a system which amplifies and announces messages to the public. It is widely used in public venues where it is required to broadcast or to inform the public. A small PA system can be used in lecture halls, churches, while a big PA system is applied in transport stations, hotels and stadiums.

The PA system includes many functions and takes hotels as an example. The functions consist of fire linkage, remote paging, television sound function, etc. The infrastructure of the typical PA system consists of speakers, amplifiers and microphones. Traditional PA systems make use of copper wire cable for communication. However, due to the emergence and widespread use of the internet, PA systems also switch into internet protocol based (IP-based). This page will discuss the details of IP-based PA system in terms of its system design, functionality and possible developments.

Audio Source
Audio sources are divided into two main groups. The first group is hard-sound sources, which are most commonly presented as electronic instruments, and have a large internal library of sound support and generally have some of the best samples on the market; the second group is soft-sound sources, which require the support of a host software to run on a MIDI interface on a computer. To be fair, the best sources can be used to achieve a falsetto effect.

Microphone
Microphone, an electro-acoustic device, is a microphone, a transducer for the conversion of sound and electricity, through the action of sound waves on electro-acoustic elements to produce voltage, which is then converted into electrical energy. It is used in various types of sound amplification equipment.

Benefit:
1. Make full use of WAN resources, you can obtain audio resources on the network anytime, anywhere. Since each terminal has an independent IP address, any terminal can be controlled to play different programs;

2. Due to the use of network transmission technology, the audio signal has no transmission interference and distortion. It adopts MP3 compression algorithm, which occupies low network bandwidth (8k-128k) and can ensure sound quality fidelity. After testing, it adopts 44.1khz 16bit sampling 128kbps rate compression passband (line output) 20-16khz, distortion ≤ 3%;

3. Simple installation. As long as each factory has the following two conditions: 1) ADSL dial-up Internet access; (2) AC 220V socket, standard Ethernet access RJ45 socket or WIFI signal;

4. Under the premise of centralized management by the broadcast system administrator, through system authorization and IP network connection, different users can arrange personalized programs through the client and play them at regular and fixed points.

Safety and Security:
Public address system has the unique advantages of point-to-point communication, flexible scheduling, easy reception and fast transmission, and is widely adopted by all countries in the world as an emergency information transmission mode. In the event of major natural disasters, emergencies, public health and social security and other sudden public crises, the function of rapid dissemination and release of corresponding information can meet the needs of governments at all levels for public emergency information release.

According to relevant communication literature, the effect of information transmission can be divided into three levels according to its logical or expressive stage: cognitive level, psychological and attitudinal level, and behavioral level. Therefore, the specific performance of emergency broadcast is: whether the emergency broadcast can be heard, the frequency of emergency broadcast, and the purpose of emergency broadcast.

For the Public address system, it is necessary to establish an operation mechanism for collecting emergency broadcast information, establish an information sharing mechanism for emergency broadcast, and carry out various emergency broadcast services. In order to protect the public address system, emerging technologies can be used to promote the multi-terminal application of emergency broadcasting. Gradually standardize the daily operation and management of emergency broadcasting, give full play to the role of releasing emergency information during major natural disasters, public health and security emergencies, ensure the normal and orderly operation of emergency broadcasting system, and improve the government's emergency management, control and response capabilities.

WIFI PA system
Existing PA system, either traditional or IP-based one, still relys on cable connection.

Traditional PA system needs various types of cables such as network cable, aux cable and power cable. For IP-based PA system, with the help of network switches, aux cable can be elimated in general. And since the speaker does not require a tremendous amountof power, by applying Power over Ethernet (PoE) to the speaker, most of the power cable can be neglected too. However, in both cases, cabling work still exists. Especially during the installation of PA system, cabling along the the room or from room to room is still a time consuming work.

As described in previous section, in a normal IP-based PA system, a network switch is connecting the control computer and other mixer amplifiers. These amplifiers are then connected to the speakers, which are located in different positions or rooms. This allow one or few controllers to control the whole PA system in a control room.

With the help of wireless technology, the PA system can be further improved by getting rid of most of the cables. Technically speaking, there are a bunch of wireless technologies which can achieve the same goal. However, since PA system is usually used within a building, sometimes outdoor but still in a closed area, WIFI is still the best choice and the easiest method to apply and modify if necessary.

A WIFI PA system is still IP-based, components within the network are still recognized by IP address. The only difference is changing the communication method into WIFI. This can be achieved by serveral ways. One of them is to set up its own WIFI network, i.e. a private WIFI network dedicated for the PA system. By connecting a a WIFI router to the swtich and all amplifiers respectively, WIFI communication is achieved. However, though simple to install, the above setup requires additional equipment which brings an increment to the cost. A more cost-effective method is to use the existing WIFI network. The equipment of PA system can still be protected by means of password or other network security measures. To make the system simpler, an all-in-one product which combine both ampifier and speaker is often used. In that case, only the power cable is left. By connecting to the nearest power source, this can be solved "locally".

A more advanced practice is to use portable WIFI speaker, which is usually equipped with internal battery. As such the speaker can function for a couple of hours in wireless connection, and un-plugged. It is especially applicable to some adhoc event in an exhibition hall or even in outdoor area where wiring a difficult.

WIFI PA system also brings advantages in terms of system control. As all component are connected wirelessly, a desktop control computer is no longer a must. Any wirless device which is connected to the network is capable to access the control page. Without a password protected account, controller can login through a laptop or mobile phone. If it is a event which covers a bigger area, controller can easily control and adjust different speakers according to their location and direction with respect to on-site conditions.

Combine with intercom system, i.e IP PBX/PABX
PA system nowadays play an important role as an announcer/performer in modern city especially in sports stadiums, hospital and other public facilities. As mentioned in the previous items, it is easy to understand that the system design and function of the PA system. Private branch exchange (PBX) is well known as a telephony/intercom system used in PA system nowadays. To carter for the continuous improvement of IP PA system, IP PBX also need to develop and implement to facilitate the new system. Implementation of IP PBX not only can enhance the PBX reliability, but also to improve the whole IP PA system performance.

As IP PA system seems become the trend of future development, IP PBX is foreseeable to be implemented into it. The IP PBX system provide voice connectivity to the user’s phone inside the building and which is known as a telecommunication device. The telephony network can be observed easily by using the internet connection. With the help of the IP network, it is simple to set up and reliable to use as it supports both online and offline mode by controlling the IP PBX panel.

Integration of intercom/telephony to IP PA system may need the components as mentioned in the above chapters such as IP speaker, server, cable, Network Host, etc. or some of the existing component need to be updated to carter for the IP PA system. IP PBX share the use of the equipment of IP PBX system such as IP speaker and server. The infrastructure also include connection cable/fiber and amplifier to make the integration be completed. The electrical setting of this basic function is simply not complicated. For the front-end user, a pair of audio lines need to connect between the system and the speaker. At the back-end, only racks with electrical set-up for the server is enough to the whole system. These components are compatible to both IP PA and IP PBX system.

One of the basic function is related to announcement/large distribution of audio information after integration. Once the installation works of the mentioned infrastructure completed, the operator can setup call group in the IP PBX server for each zone. Then the IP address of the speakers in each zone can be assigned. The operator has a call in the group by using the simply grouping.

There are benefit over using IP PBX which listed as follow:

•	As mentioned, the reliability is higher. The IP PBX will connect to the server or better to use cloud-based technology in order to transmit and receive the data by the operator. There are also multiple data center to monitor the performance. Operator can set-up zoning/groups for distribution of information. If one of the PBX network goes down, there are other groups can pick up the role of the one which malfunction.

•	The things needed to build in the system is only the basic items such as password, domain control, addresses, etc. This action can be performed in the existing IP-PA server. So that, the cost of the infrastructure would be lower in IP PBX system as only existing equipment/component used to set-up the whole network and no need to purchase another equipment. Cost can then be saved.

•	The communication cost of using IP PBX is low as the cabling work is much fewer and the material cost would be less than the traditional one.

Beside the benefit of the integration of the IP PA system and PBX system, there are still number of limitation.

•	The software included operation system and other essential software as well as the network need to update/configure regularly. This lead to an additional maintenance cost for the whole system.

•	There is no remote function for the IP PBX system. The operator cannot have the set-up at home and need to go back to office for the grouping function or even control the panel.