In your Gmail settings, click on 'Chat' to manage your 'chat' settings. Here you have the option to turn chat on or off. In addition you can
Save or not save chat history - If you save it you will be able to search for chat conversation later. You also have the option to 'go off the record' while chatting.
Auto add suggested contacts - use this to either manually manage your chat partners or allow people you communicate with often to be in your chat list.
Call Phones - enable or disable the ability to 'call phones' from your account.
Voice and Video Chat - Choose the camera, microphone and speakers you will use for your chat, video and voice contacts. Verify the working settings for each component by clicking on 'verify your settings.'
Sounds - turn notification settings on or off
Emoticons - choose whether emoticons are animated or not.