Inputs utilize 12v keying for reliability. A board typically handles 64 inputs as there are 61 keys on the typical organ manual. Outputs are open collector in most cases in order for 3.3v circuits to sink 12v loads such as lamps and relays. For moving drawknobs we recommend power MOSFET switching and will be reworking previous boards to provide drawknob level switching on single boards, likely in 32 circuit configurations. That would drive 32 SAMs with their 64 coils.