Friday, August 10, 2007

PA Paging over IP Networks

You may have heard about Voice over IP or VoIP, well now it’s paging over IP. This is a new way to page or provide an intercom over the network. But how does this all work? How does your voice get on the network? Good question.

TCP/IP network technology makes local area networks and the Internet possible. It provides the basic communication protocol that allows all the information to move between all the computers on your local area network and over the World Wide Web. Now this same technology has been used to send voice, paging and intercom messages. Here’s how it’s done.

The way it works
network audio systemFirst let’s understand some of the basics. Your voice is sound waves that are converted to electronic analog signals by a microphone. When you talk into a microphone that’s connected to your computer it’s converted to a digital signal. This is called analog to digital conversion. If you are using Voice over IP, then you may have a phone converter that does the same thing as your computer. It converts the analog signals to digital form and connects it to the network.

It’s interesting to note that the information on the network (or even over the Internet) is not sent all at once. You can start talking, and instead of sending this continuous stream of information, the information is broken up into batches or packets. It turns out that everything you do on the Internet involves packets. For example, every Web page that you receive comes as a series of packets, and every e-mail you send leaves as a series of packets. Networks that ship data around in small packets are called packet switched networks.

On the Internet, the network breaks an e-mail message and the voice message into parts of a certain size in bytes. These are the packets. Each packet carries the information that will help it get to its destination -- the sender's IP address, the intended receiver's IP address, something that tells the network how many packets this e-mail message has been broken into and the number of this particular packet. The packets carry the data in the protocols that the Internet uses: Transmission Control Protocol/Internet Protocol (TCP/IP). Each packet contains part of the body of your message. A typical packet contains perhaps 1,000 or 1,500 bytes.

OK, so now the information can get sent to another computer. Now how does this relate to a paging system? The paging system uses a special purpose computer (sometimes called an appliance because it’s very simple), to receive voice messages. Its job is to connect to the network, pick up the packets addressed to it and convert it back into analog form so it can be amplified and heard on a speaker. So the simplest paging system is a small computer with digital to analog converter, with audio amplifier and speakers connected to it. Now I can talk in one part of the building and be heard in another part of the building, or even across the world, over the Internet. Take a look at the block diagram below which shows the components inside the network attached IP amplifier.

An Intercom system is almost as simple. Now we use the same small computer (appliance) again, but add a microphone and analog to digital converter. Now I have the ability to talk both ways. It’s almost the same as using a VoIP telephone.

Components required to page and use an intercom over IP
At the school I used to go to this horrible sound would come out of a speaker on the wall. It was really almost impossible to understand. The page originated from the school office where the secretary or principal made all the announcements. This type of paging system required a central amplifier and wires that ran to each speaker. Paging and Intercom technology, just like many other products, have been transformed by TCP/IP network technology.

Using the IP network the world has changed. Now the messages travel across the network in digital form. Digital Acoustics provides a very flexible system that uses a standard PC to control paging and intercom activity. Take a look at the diagram below.

This system uses a standard computer with a sound card and microphone instead of a central amplifier. The special software allows you to send the voice data over the network to all the amplifiers and speakers attached to the network. The software allows you to select where you send your voice. It can be to just one of the speakers, any set of speakers or to all the speakers on the network.

The great thing about this type of system is that you don’t need a central location for this to work, when you use Enterprise software, you can page from any computer that runs the software. You can have multiple locations for paging and intercom control.

Paging Amplifier
The core hardware component to a paging solution is an Audio Amplifier module that connects to the network. For example the ii3-ESS can drive a single 8-Ohm speaker or multiple speakers in an array.

With the addition of a universal 25/70V transformer, a series of speakers can be powered by a single ii3-ESS, with the quantity of speakers determined by required output levels. With a maximum output of 20 watts (8 Ohms), the ii3-ESS is capable of driving paging horns with sound pressure levels in excess of 120 db SPL. For low output applications (<8>8 watts) an external power supply is required.

Every acoustic environment is unique and using the right speakers is important in providing intelligible public address solutions. There are a wide range of speakers available from companies such as Quam-Nichols. For example:
  • 8" Ceiling Mounts - Round and Square
  • Surface Mounted Enclosures - Square and Sloped
  • Internal Horns
  • External Paging Horns
  • Corrections Grade Solutions (Vandal Proof)
  • Weather Proof & Flame-retardant
You can also use standard PA systems to amplify and provide high quality sound to large meeting areas.

Intercom Units
The ii3-EDW, ii3-ESW intercom units are examples of intercoms that attach to the network. They used on a desktop or attached to a wall. Features include:
  • High quality integrated speaker and microphone
  • Four button controls include Volume Up/Down, Monitor/Open, and Push-to-Talk
  • Four LED indicators include Active, Link, Monitor and Talk

Talkmaster-eeThe software controls everything and allows you to talk to all the attached locations on the network. For example, the following software from Digital Acoustics makes it very easy to page and provide the intercom.

The software allows you to manage ii3 Intercoms from any PC. It also allows you to easily configure intercoms, control communications and archive audio files. TalkMaster-LE software is included with the purchase of any ii3 IP Intercom and makes for a total monitoring solution.
  • Selective or master call to page all stations
  • Master control and auto detection (integrated UDP polling)
  • Provides remote door release and GPIO control
  • Allows you to record, log and archive audio sessions
  • Audio file playback (.WAV)
  • Remote and local digital volume control
  • Supports primary and secondary consoles
  • iTalk/X Active X Software Development Kit (SDK) for custom integration
For sophisticated users and applications, there’s a more advanced software product called TalkMaster Enterprise Edition. This allows you to set up multiple control points for paging and intercom activity and in general provides flexibility in addressing the special needs of complex, multi-station, multi-operator and multi-site installations.

If you need some help designing your system, don’t hesitate to contact us. We can be reached at 914-944-3425 or 800-431-1658 or just use our contact form to get information.


Pathane Wadler said...

I'm surprised that this isn't as complicated as it looks. I think a lot of establishments are using this system these days. Indeed, the paging system has gone a long way since it all started way, way back.

-Pathane Wadler

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Zhang Ying said...

Planning to get a public address system in Singapore. I just want to know any tips on choosing a public address system. Any info is a great help. Thanks.