The s5 board is the timer,display board. The board is set up for only 8 landings. If you have a group with more than eight landings then there will be another timer,display board in the s4 slot. The only circuits that will be utilized by this board will be the extra hall and car call dropping circuits. If you have a problem with the board in s5 and also have a board in s4 then you can swap them while you work on the problem board, you just wont have any hall calls at the extra floors beyond 8.
If you only have 8 floors than you will only have one s5 timer,display board and if you remove this board from the main car you will lose hall calls, you would have to take a board from another car and put in the main controller to have calls while you fix the bad one.
