In a Symphony chat, users can disable their input (Figure 1):
Figure 1 Disable Input
Disabling input prevents the user from sending any messages, chimes or attachments in that chat (Figure 2):
Figure 2 Input Disabled
A user may choose to do this to prevent themselves accidentally sending messages in a room they don't want to (such as very large or high-profile rooms).
If a user wishes to re-enable input, simple click the Input disabled icon again and the block on sending messages will be removed (Figure 3):
Figure 3 Enable Input