Here's how to enable Push-to-talk mode for voice chats on the Steam client:
Click on Steam Menu > Settings
Go to the Voice section.
For "When voice chat is active" select "Use a push to talk key to transmit voice".
Assign a key to toggle voice chat On/Off.
Click on OK to validate.
CCM is a leading international tech website. Our content is written in collaboration with IT experts, under the direction of Jeff Pillou, founder of CCM.net. CCM reaches more than 50 million unique visitors per month and is available in 11 languages.