• In order to receive audio, there must be either a speaker or a pair of headphones connected to your computer.

 
• In order to transmit audio, you must have a microphone plugged into your computer.

 
• It is recommended that headphones are used in preference to speakers. Using headphones allows you to listen and talk at the same time (this is known as full duplex audio). Without the use of headphones the output from the speakers can interfere with the microphone, causing unpleasant feedback. The only way of avoiding this is either to use an echo canceller, or to switch to half duplex audio, which means that you can only speak or listen at any one time, i.e. you cannot listen to others when you speak, or you cannot speak when you are listening. This is unnatural and can make conversation difficult.

Starting up RAT

There are two ways of starting up RAT:- from the command line and from SDR. Using SDR is easier as it automatically configures the tool for use.
 

1. Using SDR (RECOMMENDED) - Click on the session advertisement, a box will appear listing the available tools for the session. Either click on the 'Join' button which will start all the tools, or click on the tool buttons individually to the left of the screen.

 
2. From the Command Line - As with the other Mbone tools the format for setting up RAT from the command line is as follows:
Unix:
Prompt> rat [options] <address/port>

Windows95/98/NT:
Click on the Start button in the bottom left hand corner of the screen. Select Run... In the Run Window, type the following in the open: field.
Open: rat [options] <address/port>

e.g. for a session using the address 224.2.2.2, and port 2222 with a ttl of 47, the correct syntax would be:-
 

rat -t 47 224.2.2.2/2222
**All participants must use the same multicast address and port number in order to talk to one another** 

If you can't hear other people: 
 

• Make sure that the left mute button is not pressed down. When the mute button is pressed down, the icon (depicting either a speaker, headphones, or the symbol for line out), will appear inside a grey box, and the audio will be muted. 

 
• Make sure that someone is actually talking. You can see that someone is talking when the left power meter in the RAT audio window is going up and down.

 
• Make sure that the volume of the speaker or headphones is not 0. The volume can be adjusted on the slider bar next to the left power meter. 

 
• Make sure that the button with the little icon under the left mute button is depicting headsets if using headsets, and speakers if using speakers. You can change between headsets, speakers and line-out by clicking on the button with the icon. (Some audio cards will automatically send audio to headsets if they are plugged in and speakers if not. In this case, the button will not toggle, but will always display a speaker)

 
• Check that your headsets are plugged into the computer correctly. 

Further Information

The RAT userguide is available in word7, postscript and pdf format. Please refer to this for more detailed information regarding technical definitions.

There is also a RAT FAQ which answers many questions about hardware compatibility and general user problems.

Please consult these two sources of reference first. If your query still remains unanswered, please send an email to rat-trap@cs.ucl.ac.uk