When using the Cosmac VIP (with VP590 or VP580), RCA Studio II, RCA Studio III / Victory MPT-02 and Visicom COM-100 emulators a second keypad is or can be configured. In this mode a button 'Switch pad' (yellow ellipse) will be available to switch from keypad A to B and back. Note that the 'on Character' button for the VIP keypad B will map all keys to the PC numeric keypad.
The example above shows the key map for the Cosmac VIP with the VP580 Expansion Keypad configured. The header in the orange ellipse indicates that the second pad called 'B' is shown. Each keypad both A and B have the option to define 2 sets (1 and 2), see Auto and Arcade Key Definition chapter