Apple IIe Card - Manual (Page 32)

2. Connect the UniDisk 3.5 Drive cable to the larger of the two
remaining connectors on the Y-shaped cable, as shown in
the figure.
Again, be sure the connectors line up correctly, and tighten the
connector screws to ensure a proper fit.
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Warning: If you want to swap drives or devices connected to the
Y-shaped cable, be sure to turn off the computer first. If you change
devices while the computer is on, you may damage the device or
the computer, or both.
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Chapter 1: Preparing the Equipment 16