I sometimes see a thing in TV control rooms (I think it is on the production switcher) - a black lever or “throttle”-like device that is pushed forward. Does anyone know what this is called and what it is for. This is a picture showing it:
http://www.bvisions.co.za/images/p_kalypso.jpg
It is the thing in the forwards position in the top left of the picture. I have often seen these being used, and want to know what its purpose is, and why there are often several of them.
Isn’t that the vision switcher that swaps between live and preview?
The throttle levers are used for transitions, generally between what you’ve got set up on the “live” bus and the “preview” bus. Move the throttle to the other position, and you switch the busses so the live one becomes preview and the preview goes live on the air. The fancier the switcher, the more transition options you have, such as dissolves, wipes, and so forth. For really fancy switchers, you may have several busses and sub-busses which can all be layered on top of each other with various keying effects.
The throttle control is used so the operator can move it as smoothly as possible.
Most of the time, however, you just press a button because you want an instantaneous cut.