0 Transistor Switching

I was getting caught up on some of my notebook sketches and decided that these would be good to share. I use these quite often with micro controllers and hijacking a output from other devices.
You can replace the relay coil with a LED for example.

The whole idea is to be able to take a TTL level output and switch a larger load.
You can substitute just about all the components based on the Hfe of the transistor and/or input voltage you have. 
The main point is to keep the transistor in saturation. You get the idea.......

73's
Jon N5JLD