You can add unlimited wired door contacts to existing wireless dc via bus inside the contact and you can add aditional wireless siren 868mhz or wire it to existing internal siren on the pcb (only 2 legs) there is also tamper sw connection inside to extend it. I got ashock sensor for the garage door in addition to the door contact which piggy backs to the wireless dc. All working fine. I had no response about the fw yet