reference the photo in post one.

Two IO's are shown for each button on the print. The button grounds the input, which latches a register bit associated with the call in software in the group controller, and then the software latches the output on an IO board in the group controller to keep the lamp in the button lit... all this, so long as at least one car is in the group, available to answer the call.

The call itself is latched in the group software until a car responds by updating it's car position to that floor, and tells the group controller it's answering the hall call. This is what cancels the caall. The car communicates to group controller via serial comm.

The only way you see this in software is looking at the RAM address associated each particular group of calls, and decode the bit pattern in your head. Each bit represents a specific hall call. Otherwise, you can monitor the hall call test on a PC or OMT depending on what's available to you.