Depending upon Stock or the mod, the <Backspace> "pauses" the game at "0"TC, while some mods have the number keypad's <Enter> key set to send you back to 1xTC. You can also edit the "Data / Cfg / Commands.cfg" and do it yourself. I usually end up messing that up though, misplacing commas and semi-colons...

so the Backspace is my key.