R12: customizing using MENU1-15 instead of SPECIAL1-15

Selecting menu entry SPECIALx (where x is 1 through 15) causes SPECIALx event to be sent to the custom.pll.

However, the customer is working on a customization and the same does not hold true for menu1.

There is documentation stating SPECIALx will and will not be sent as an event to custom.pll.

I cannot find documentation about menu1 being passed to the custom.pll.  Also, documentation recommends using MENUx to avoid oracle's use of SPECIALx.

can you comment on any documentation or instructions on its use