access control/intercom/intercom handsets

[lomb]

if i only want a single button outside but several handsets inside and that they all ring do i just wire for a single cat 5 cable between handsets so all in series? how many handsets can one put on the same line? persumably there is a limit?also in future if i want to upgrade to a camera type intercom and screens on the handset what cable do i use for this? many thanks in advance

 

[breezer]

best asking the maker of said kit