User:U3573709/IP based public address system

The IP based Public Address System is a kind of Public Address (PA) System which with uses an Internet Protocol Network (IP network). Similar to the conventional PA system, it also concludes multiple loudspeakers, amplifier, mixer and microphones. For the IP based system, the amplifier and mixer should be supported by Internet Protocol so that digital audio streams can be transmitted and received through the network.

With the reach of the IP network, the audio signal to paging location can be distributed through the network by the network-attached central amplifier. The digital audio stream will be sent via the Local Area Network (LAN) by the transmission of the application of control computer and the specialised intercom components like IP speakers will receive the digital audio streams and convert these streams to analog signal for producing the apparent volume of a sound, like human voices, musics etc.

The IP based PA system is considered as a more cost-saving and reliable PA system compares to the conventional PA system, by the reduction of cost in electrical connection and its stability. By taking advantage of tendency of Internet of Thing (IoT) and the stability of IP based PA system, replacement of the conventional PA system to the IP based PA system is considered as a new trend of the PA system development.

Background
With the development of technology, people's quality of life has improved. Many public places are always very high density of people flow. Such as large shopping malls, opera houses, concert halls, etc. in urban commercial areas. With the development of electronic technology, PA system is slowly created, which includes microphone, amplifier and loudspeaker, which can amplify electronic sound and distribute it to different amplifiers. For such entertainment venues as concert halls, PA systems undoubtedly provide a better listening experience for the audience, and PA systems create a better artistic atmosphere by adjusting the volume. In addition to the entertainment function, the PA system is more useful for public broadcasting. For example, if an emergency occurs in a shopping mall, the PA system can send an alert to people to evacuate in time. But PA system usually has its limitations, such as transmitting information accurately, transmitting signal distortion and other problems. So building the PA system on top of IP network can enhance the function of PA system. Using TCP/IP protocol, deploying audio, speakers and other devices on IP network can transmit rapid, accurate signals with little signal distortion. At the same time, with an IP-based PA system, you can even ensure security for the signals transmitted by the PA system.

Different types of PA Systems
The types of PA systems are based on the location of system installation, the type of software, the number of users, so on.

1). Small Public Address Sound System

The small PA system simply consists of a microphone, one or more speakers and an amplifier. It can be a portable system as it is normally battery-powered like the iconic “megaphone” or “bull horn”. A sound source such as a streaming device, mp3 player, compact disc player, or radio may also be associated with a PA system so that music can be played for audience members. It is suitable for small venues such as meeting rooms, churches, classrooms. However, the audio reliability may be affected because the system is adjusted for speech.

2). Large Distributed Public Address System

The large distributed PA system is similar to a smaller PA system. However, it required more amplifiers for provided high power at high voltage. The high voltage is transmitted through hundreds or thousands of loudspeakers distributed in multiple locations. Each loudspeaker needs a transformer between its voice coil and the amplifier to decrease the voltage on the speaker field. It is suitable for the hospitality industry, for example. Hoteliers could assign to small speakers throughout the hotel rooms, lounges, halls.

3). Telephone Paging Systems in PA Systems

It connects the PA system amplifiers and speakers to the telephone. A paging proclamation can appropriately be made from any telephone device connected to the phone system. When a user speaks a message on the telephone, the networking speakers will broadcast the message. Therefore, there is no requirement for an additional microphone and installation of conceivable expensive cables.

4.)IP based public address system

Instead of a central amplifier, this system indicates PA paging and intercom systems that use an Internet Protocol (IP) network to deliver the audio signal to various locations across a building or campus that contain the IP network. Network-attached amplifiers are utilized to communicate between the users. At the transmission end, a computer transmits a digital audio signal via the local area network, using audio from the computer’s sound card or from stored audio recordings. At the receiving end, particular intercom modules combined with a traditional loudspeaker receive these network transmissions and reproduce the analog audio signal.

5.) Wireless Mobile Telephony PA Systems

It applies the existing wireless mobile telephony systems like GSM networks instead of a centralized amplifier to deliver the audio signal to paging positions. The GSM mobile Networks are utilized to communicate between the users. At the transmission side, a PSTN Telephone, mobile phone, VOIP phone or any other communication device that can gain access to make audio calls to a GSM-based mobile SIM card and communicate with it. At the receiving side, a GSM transceiver receives the response of network transmissions and reproduces the analogue audio signal via the PA system.

Limitation of Currents PA Systems
1). Backward technology, poor compatibility and scalability

The existing broadcasting basically adopts analog transmission and manual management. The system is susceptible to environmental interference and crosstalk is easy to occur in multi-channel broadcasting. Unable to realize digital format (MP3) audio files in the terminal directly play, unable to connect with IP network, in order to truly realize the digital audio source, play management automation.

2). Poor sound quality and single function

Broadcast equipment can only be used for background music, broadcast announcements and other activities in the area, which cannot meet the needs of remote unified broadcast of the plant, and cannot make the company's managers speak to all the plants at the same time.

3). Complex installation, inconvenient maintenance and high failure rate

Because fixed-voltage cable broadcasting is configured strictly according to the principle of impedance and power matching, the power amplifier is often burned out due to the failure of a transformer or speaker box, affecting the whole broadcasting.

4). Poor manageability and remote control

Because only in special device (tape, disc, CD machine, etc.) and store the computer as a source of sound of MP3 files, need of personnel in a special location management broadcast content, so we can not use modern technology to effective management of broadcasting audio source, more cannot be played for remote control, flexible application of the broadcasting system, cause the waste of resources.

Development of IP Based PA System
The development of PA systems has gone through three stages: the analog system stage, the digital system stage and the IP system stage.

The PA system in the analog system stage is mainly used in buildings with simple structures, where only the same audio source can be played in the area within the broadcast system. The PA host of the analog system transmits the audio source equipment and fire alarm signal to the functional amplifier through analog audio, and then plays through the speaker. The analog audio line cannot share the same cable channel with the weak power cable, and needs to lay a separate bridge, and the wiring construction is complicated. Therefore, it is only suitable for small-scale public broadcasting area.

When the building needs to play different audio in different zones, the PA system of digital stage comes into being. The digital stage PA system uses digital matrix to convert the audio source and signal into analog and digital and then transmit it to different functional amplifiers through the broadcast bus, and finally play the sound with the speakers. The use of digital partition management allows different areas to play different sounds. However, the wiring complexity of this stage is no less than the PA system under the analog system.

When technology has developed to the IP stage, PA systems are not only less complicated to wire than before, they also have advantages such as good interoperability. The IP-based PA system digitally encodes and transmits signals such as audio source devices and fire alarms using an Ethernet network, decodes them with a decoder, and finally converts the data into an analog signal and connects it to a functional amplifier, which is then played back with speakers. As long as by Ethernet, this mode of PA system can be broadcast.

General System Design
The design of the IP based PA system can be diverse, depending on the usage and the site environment. The diagram below shows a general design of an IP based PA system in different criteria.

Common Equipment
Below are the common types of equipment involved in a general IP based PA system:

Remote Control Unit
The remote control unit can be a computer or a server. It can act as a network management system for managing the components of the PA system inside the same network.

IP Paging
It is a IP based paging station and can connect to the PA system through the IP network.

Network Decoder
The network decoder acts as an adaptor between the LAN or Internet and the typical power amplifier. It allows the existing typical PA devices to merged with the new IP based PA system, where the end device need not be replaced.

Network Amplifier
The network amplifier is like a combination of the network decoder and the power amplifier. Existing speakers can be paired up by the network amplifier to create a modern IP paging system.

IP Based Speake r
The IP based speaker is based on TCP/IP protocol and can operate without amplifier. It transfers audio signal and control signal via network cable. In practical, the end devices would connect to a common switch before entering the LAN or Internet.

PoE Supported Speaker
This type of speakers is also IP based, while it can be powered by POE. A PoE switch would be used to supply power and transfer data to the end devices. Since only one data cable is needed for each of the device to operate, it can save cable laying and it is more convenient to arrange zones for installation.

Cost reduction
IP-based PA system is possible to reduce the cost of cabling. Advanced IP-based PA system is able to reach the field devices under the same coverage of network through WIFI. It provides another way for communication between the field device and the core units. Costs for the connection cable, cable containment, and cabling work are reduced comparing with the traditional PA system (in the case of large-scale PA system). For a traditional public address system, a coaxial cable is needed for the connection between the amplifier and all the speakers. Some areas are difficult to reach through wire due to the restriction of site condition, containment, or routing.

Reliability
PA system reliability is the most important part of the core of the whole system as the PA system is critical during life-threatening situations like a fire outbreak. Immediate evacuation announcement is the key to saving hundreds and thousands of lives. Therefore, reliability and redundancy take the most important role in the PA system and that is the part that IP-based PA system is better than older analog PA system.

For the traditional PA system, an outage of amplifiers is a terrible situation without another redundant amplifier in the affected zone. The whole zone would go silent without any notice until someone spotted the problem is reported by the users. Even if the malfunction is reported immediately, repair or replacement of the device is not easy and time-consuming.

IP-based PA system is hard to tolerate or ignore any single-paged announcement even when the paging system is down or out. With the advantage of a network-based system, all amplifiers are decentralized, and paging console stations are interconnected. A Digital IP PA system consists of a great number of distributed amplifiers. The IP devices are all connected to the same network no matter how far they are physically separated. All audio signal is digitized and directed to the specific amplifiers. Since the PA zones are able to change and configure dynamically through the control software, the affected zones can still remain functional. Therefore, the system can still broadcast the announcement even when the associated amplifier is down. Moreover, having a backup control station can further enhance the reliability to prevent the case that the primary control station is down.

Decentralization
Fault management

IP-based public address systems provide high transparency for personnel to monitor since each IP speaker has an individual assigned IP address and the IP amplifier is linked with a single speaker or a small party of speakers. The whole infrastructure is communicating through the network so that the instant status of the devices is under the eye of the central control panel. With the help of a monitoring system, the control room will be alerted and sent out a support team immediately when a fault occurs.

Audio alignment

IP-based PA systems are communicated through networks and the performance is different from the traditional PA system in aspects of transmission speed and stability. Unsynchronized announcement made by two different zones can easily be spotted by human ears and brings unfavorable experience. IP-based PA system does not restrict by the zone as different zone is not connected with different speaker chain but network. Command and signal received by the adjacent zones are almost at the same time.

Integration
IP-based PA systems can integrate with another system as the devices are all IP-related. While the core units are decentralized, the communication system is still connected closely. It allows communications systems such as IP phone for paging and call to be covered in a single system. A wide range of IP equipment including IP intercoms, alarm systems, sound-to-text translation, sensors, etc. are able to interface with each other in the PA system to perform a variety of functions. Benefitting from the trend of IoT and smart living, IP-based PA system provides more flexibility and function to the industry.

Unicasting and Multicasting
Unicast IP is delivered on a 1-to-1 basis. It is more common that the IP PBX is the source of it. To create a multicasting signal, it requires the user to dial an extension or a page group on the PBX to set up a paging command. However, there is a limitation on resources for the PBX as it is initiating a number amount of SIP calls to set up the page depending on the number of endpoints. IP-based PA system is able to achieve the same result without compromising any resources on PBX as each endpoint is set up with a multicast IP address like a channel that is always listening to the incoming signal. The user just needs to make 1 SIP call to the multicasting IP address and all listening endpoints will receive the audio signal and broadcast the audio. Apart from multicasting, unicasting is also easy to perform. As each endpoint has its unique IP address, messages can be easily confined to the intended audience. This makes the tool useful in a broader range of situations.

Limitations
Although significant benefits has provided by utilising Internet protocol (IP) in a Public Address (PA) system, there are a huge gap that the IP based PA system can substitute the conventional system due to the following limitations and concerns:

1. Limitation due to the Cable for network connection

The network connection in a IP based Public Address system may require wire or wireless connection. For the wired connection, CAT-5 and CAT-6 are the most popular category of cable using for connecting between devices in a network. However, the maximum cable distance that these cable can travel are only 100 metres (330 fts). The cable limits the IP based system in used in a large venue or site which becomes an obstacle for the system be widely in used.

2. Concern in Power consumption

The devices in a IP based PA system are required 24/7 power supply for maintaining the stability of IP network and ensuring all devices are reachable. However, the 24/7 power supply may increase the uses of power consumption compare to the conventional PA system, the lower efficiency may consequently increase costs in electricity. The potential cost increase is a great concern for the users not to choose the new IP based PA system.

3. Concern in Network Reliability

The network in the IP based PA system is essential of its function. However, the strength of the network indicates the time that commands to devices executed the commands （i.e. time needs from sender to receiver). The broken connection may interrupt system and functions of system are affected.

To ensure the reliability of the system, maintenance of the cable connection is important. Compare to the conventional PA system, the extra routine network test for the CAT-5 and CAT-6 cable is required to ensure all devices are reachable inside a network.

4. Concern in Network Security

Security is essential to the Public Address System especially in the critical site like Airport. The most prominent security issues over IP based Public Address System are identity and service theft, viruses and malware, denial of service, spamming, call tampering and phishing attacks. Threats of IP based PA system is relative higher compare to the conventional PA system, as the attack can be taken through the network instead. These kind of attacks may interrupt the PA system which causes the threatening to the users and the receiver are not able to receive the emergency or update warnings. These kind of threatening may consequent the human injury and capital loss. The potential threats is important for the owner and users and it is a concern for the users not to choose the new IP based PA system.

Current and Future Application
IP speaker is deployed on the IP network to provide reliable, fast and automatic announcements by TCP/IP protocol. It is simple to manage through a standard PC and application.Communication data is secured to reach anywhere in our network or even internet, and offers high definition encoded voice / audio without transmission impairments and distortion of audio signal.

Similarly, IP based public address system can realize the function of tranditional public address system, that is, long-distance broadcast notification or background music in public places. Therefore, this technology can be applied to urban dense residential areas, remote rural settlements, schools, hotels, supermarkets, parks, squares and other occasions. Background music can be played in daily life to create a relaxed atmosphere. In emergency situations, it can be broadcast notice, and guide people to avoid risk. Especially in schools, this technology can be applied to teaching activities such as exercises, bell ringing for classes, which can effectively improve the teaching experience of both teachers and students.

At present, mobile phones have become an integral part of modern people's daily life. Therefore, on this basis, the IP based public address system can cover most people through the network. With the help of IP based public address system, if an emergency occurs, people can quickly and accurately deliver their safety shunt guidance by the broadcast based on the IP network. Users are able to get information from their IP phone. Then, IP Speaker will have a remote control to the situation.