What Is An A/B Direct Switcher - Blackmagicdesign ATEM Television Studio Installation And Operation Manual

Getting Started
9

What is an A/B Direct Switcher?

If you have been using video switchers for a long time, then you might be used to older-style A/B direct
switchers and you can easily set your ATEM switcher to A/B direct switching in the ATEM software preferences.
See the Transition Control section of this instruction manual for details about where to change this setting.
A/B direct switchers have an A bus and a B bus. One bus is the program bus which shows a red button for
the current program output. The other is the preview bus which has a green button for the preview video.
As you move the fader bar up and down, the buses switch so that the red program button follows the fader
handle. This is where A/B direct switching is really easy to use as the buttons stay lit in the same positions
and just switch color between green and red.
A/B direct switching becomes a little more confusing when the fader bar is not used to make the switch.
If you use a cut or auto transition button to bring your preview source on air, or if you use more than one
control panel connected to your switcher, the fader bar won't have moved on the control panel that you are
using. The red program output always follows the fader bar handle and, as you haven't moved it, the red
program light has to move to another button on the same row and the green preview light has to move to
another button in its row.
This can become quite confusing when sometimes using the fader bar to make switches, and sometimes
not, as the rows containing your preview and program buttons will sometimes switch and sometimes stay
where they are which has the potential to lead to mistakes.
This is why modern M/E style switching is preferable because you'll always find your green preview button
in the row labelled Preview, and the red program button in the row labelled Program. It's always consistent
and there are no surprises with M/E style switching.