HP 54721A User Reference page 10

Channel Setup Menu
At the top of the piug-in is the Channel-Setup hardkey. This hardkey
gives you access to the channel menu for the plug-in. The channel
menu is a softkey menu that comes up on the right side of the display
when you press the Channel-Setup hardkey. You will also notice that
there are several types of softkeys available. A description of how
each softkey functions is given in the User's Quick Start Guide that
was supplied with the mainframe.
Figure 1 is the menu map of the channel-setup hardkey.
Figure 1
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