Callwaiting tone

Hi all,

I’m using Asterisk 1.4.17 with FreePBX I have activated CallWaiting option in the configured extensions since voip phones support until 5 lines.

When users are talking they often listen a very irritating tone that difficults conversation. I would like to avoid it but I’m not sure what is generating it. I think that it could be related with FreePBX’s CallWaiting feature. What do you think? If it’s the case I could mantain the CallWaiting feature avoiding CallWaiting indication?