..........Software ISDN Audio Codec for PC
...............Software Audio over Network for PC
........Software Audio over DSL, ADSL and Internet

AudioTX Communicator Manual

2. Using AudioTX Communicator
2.1 ISDN connections
        - General information
        - Phonebook entries
        - Making and receiving ISDN calls
2.2 Network connections
        - General information
        - Phonebook entries
        - Making and receiving network connections
2.3 Internet & public network connections
        - Bandwidth considerations
        - Connecting through a proxy server or firewall

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AudioTX Communicator connects to all of the other main ISDN codecs available on the market today. Communicator's unique adaptive auto-connect technology means that these connections are simple and trouble-free.

The first stage in dialling a connection is to create a phonebook entry. This stores the phone numbers and settings used together under a unique name that you provide for the connection. Any of the phonebook entries in your list can be dialled by simply selecting the entry and clicking on 'Dial'.

You'll find this process so simple that you won't really need to refer to these instructions, but here's a step-by-step guide to walk you through your first connection.

First: Click on the 'Add' button to the right of the main screen. The 'Add new phonebook entry' window appears:

Connection Name First type a name for your new entry - this will be the name shown in your phonebook. Number of Channels & Phone numbers Select the number of channels for this connection (64 or 128kbits) and enter the phone numbers. If you are using 2 channels and leave the second number box blank, AudioTX copies the number from the first box when you click OK.

Type of compression, samplerate and audio mode Choose from MPEG Layer II, MPEG layer III and G.722 coding depending on the codec you are connecting to and the mode it is expecting. G.711 is a special case and can be used to call into a normal analog telephone (like a telebalance unit). Sample Rate: 48kHz is the normal setting, though using 24kHz provides better quality on MPEG2 at 64kbits (1 channel). Audio mode: the best options are normally Mono or Joint-Stereo - If you only need Mono, you'll find that selecting a stereo mode will reduce your audio quality as both codecs have to code for stereo and this wastes the available space on the link.

Saving the entry When you have finished, click OK to save the entry and return to the main window.

Making and receiving ISDN calls

Make sure that your new entry is highlighted and click on the 'Dial' button at the bottom right of the main window. Watch the connection box at the top left of the screen and the status bar at the very bottom to see your connection progress. You should see the following sequence in the status bar and appropriate changes to the Connection box:

Connecting to: (ISDN) 1234 5678 (the ISDN number)
Connected to: (ISDN) 1234 5678

Within a few seconds of this sequence, you should see information in the 'Receiving' and 'Transmitting' sections of the Connection box.

The final stage is that the peak meters start moving (or the bottom green LED lights on each if there is no audio being sent ot received.)

Incoming calls are automatically accepted and auto-detected. You can modify this behaviour using the Answer Settings window discussed in section 3.

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AudioTX Communicator is able to send and receive live audio over IP networks. Depending on the network bandwidth available, you can use MPEG2, MPEG 3 coding up to maximum bitrates of 384 kbits and 320 kbits respectively. You can also send and receive UNCOMPRESSED (Linear PCM) audio. A 48kHz sampled stereo signal (above CD quality) requires 1.5Mbits - which is quite possible on most company networks.

This includes the following:

A standard office or company-wide PC CAT5 network, either 10 or 100Mbits
Leased line connections
ADSL, DSL and cable-modem links
Satellite links
ATM networks

The PCs running communicator at each end can have a standard Ethernet network card installed, or may have different larger-scale networking hardware (say an ATM or Gigabit Ethernet card)... both options are fine. As long as the network is available to the Windows operating system, AudioTX recognises it and will allow connections.

Communicator has three distinct network modes, which are explained in more detail below. Each has a different degree of safety margin built in to deal with any holdups in sending or receiving audio across the network:

Connections over public networks (e.g. Internet) are discussed in more detail in the next part of this section.

Each of these settings should be used for guidance only. For example, you may decide to use the middle setting even on a well-managed private network if you are carrying a live transmission. You may be able to use the middle or even the lowest setting on your internet connection if your provider happens to have a very clean route to your chosen destination.

As with ISDN connections, the first stage in dialling a connection is to create a phonebook entry. This stores the phone numbers and settings used together under a unique name that you provide for the connection. Any of the phonebook entries in your list can be dialled by simply selecting the entry and clicking on 'Dial'.

First: Click on the 'Add' button to the right of the main screen. The 'Add new phonebook entry' window appears:

Connection Name First type a name for your new entry - this will be the name shown in your phonebook. Address and port You can enter an IP address or computer name or FQDN (e.g. studio1.tx.radio.net) depending on how your network is configured. The port number must be the same as you have set in the answer settings of the AudioTX device you are calling. 5003 is used as the default.

Type of compression, samplerate and audio mode Choose from MPEG Layer II or MPEG layer III coding or Uncompressed (linear) audio depending on the available network bandwidth. Sample Rate: 48kHz is the normal setting, though using 24kHz provides better quality on low bitrate MPEG2 at 64kbits or less. Audio mode: For MPEG2 and MPEG3 at lower bitrates (<192) use Mono or Joint-Stereo. For greater bitrates (and always for linear) you can use Stereo coding which will provide better audio quality at higher bitrates.

Saving the entry When you have finished, click OK to save the entry and return to the main window.

Making and receiving IP Network connections

Make sure that your new entry is highlighted and click on the 'Connect' button at the bottom right of the main window. Watch the connection box at the top left of the screen and the status bar at the very bottom to see your connection progress. You should see the following sequence in the status bar and appropriate changes to the Connection box:

Connecting to: (IP) 10.10.10.23 (the name or IP address)
Connected to: (IP) Studio area A (the ID string set in global settings at the remote end)
(In the case of a connection using the Internet/Busy network option, you will first see the line tests in the status bar).

Within a few seconds of this sequence, you should see information in the 'Receiving' and 'Transmitting' sections of the Connection box.

The status bar then shows transmit and receive bitrates (together with transmission performance percentages for Internet/Busy network setting).

The final stage is that the peak meters start moving (or the bottom green LED lights on each if there is no audio being sent ot received.)

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As part of its IP Network transmission capability, Communicator is able to establish live audio links over the Internet - whether you have an ASDL connection, DSL, Cable-Modem, Leased line, or other high speed connection.

In planning your use, you should first check what the theoretically available bandwidth is - for example, many European providers sell a 512kbits ASDL or Cable modem product... however you may find that they only provide that speed downstream (i.e. to you) and the upstream speed (i.e. away from you) is 256kbits or even 128kbits. You should also check what bandwidth you are also getting practically in day to day useage of the link. There are many internet sites and tools that can help you do this.

Typically Communicator will be able to use a bitrate of between 10 and 20% less than this maximum.

All you then need to do is to establish the IP address of the remote PC running AudioTX that you are connecting to and follow the standard instructions for Network connections. The three different network modes detailed in the table in section 2.2 are worth experimenting with - depending on your needs, you may not need to use the official 'Internet' mode and so may end up with a much shorter delay in transmission.

If you do not have a fixed IP as part of your service, again there are free programs which will allow you to look this up each time you use the system. You may find in the longer term that it's worth asking your provider for a fixed IP address.

Connecting through a proxy server or firewall

If your network has a proxy server or firewall, you need to discuss this with your network administrator in order to allow AudioTX Communicator to function correctly. There are several possible options:

To make outgoing calls:

• The best option, if your firewall supports it is to use a SOCKS proxy. You will need to talk to your network admin or IT department about this. You will then also need a socks client installed on your machine (see the list at the end of this section).
• Open a TCP bridge on port 5003 to allow you to make outgoing connections to a particular destination PC and port. You can of course use specify a different port number in the phonebook entry as long as this matches with your firewall settings and the port setup in the remote PC's Global Settings Window (see section 3)

To receive incoming connections:

• Open a reverse TCP bridge on port 5003 (directed to the AudioTX PC) to allow you to receive calls. You can of course set a different port number in the Global Settings Window (see section 3) as long as you tell people calling you what port you are using.
• If you have multiple AudioTX PC's behind your firewall, open a new Reverse TCP Bridge mapping on a different port for each and set the port in the Global Settings of each PC to the correct port.

Suggested SOCKS Proxy clients:

Hummingbird Socks - (FREE) This adds SOCKS to all network activity on your machine, though you can exclude certain ranges which you tell the software belong to your internal network. All other traffic is then directed via your SOCKS proxy server. (Company home page: http://www.hummingbird.com).

SocksCap - (FREE) This installs an 'application launcher' for programs which need to channel network traffic through a SOCKS proxy. (By NEC, Company home page: http://www.socks.nec.com)

eBorder client - (Paid for but not expensive) The professional version of NEC's SOCKS client which works in a similar way to the Hummingbird product. (Company home page: http://www.eborder.nec.com)

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