Massey Plugins' Talkback is a unique and really helpful plug-in that is seen as part of Massey's Tools collection of free plug-ins. I don't know the full scope of compatibility these plug-ins span but they're at least available for Pro Tools and I'd imagine that most DAW's will run it. What Talkback does is a really simple and helpful thing - it will mute your talkback mic while recording is happening and turn it on while it's not and communication between the live room and the control room is needed. Simply stick this on your talkback track in Pro Tools or whatever DAW your using, and it will do it's thing! There's a meter in it to show the level of your talkback mic and you can also adjust this level in the plug-in itself. Besides that, there's literally nothing else in the plug-in, so it's definitely one of the utility plug-ins that will do what it does and that's it. There's nothing to using it, so I doubt a manual was even made...
Right now I've got the Massey Plugins Talkback plug-in on my system at home. This DAW is Pro Tools 9 based and runs on a Mac Book Pro lap top with a 2.2 Ghz Intel Core 2 Duo processor and 4 GB of RAM, while I'm running Pro Tools with a Digi 002R audio interface. However, I rarely use the plug-in in this setting as it's not necessary for me in my small home studio. I've used it much more in larger home studios and professional studios which are running Pro Tools HD where I've never had a problem at all with it. If you're system can't handle this one, you've probably got bigger problems than running this plug-in.
Massey Plugins Talkback is one that every studio should have where a talkback microphone is being used. Without it you run the risk of having bleed from the talkback mic in the headphones of those who are playing while recording, or muting it manually yourself which can be annoying and/or you may forget to do it. With Talkback, just throw the plug-in up and have it do it for you without ever having to think about it again. It's free, so there's really no excuse for not having!