The equipment needed to operate an Online Radio station is not very different from that needed to operate any other radio station. Online Radio can broadcast with considerably less.
NOT needed for online radio is an aerial or a transmitter, as the programme is sent down links to servers, which relay it onto the internet, via networks of fibre, microwaves and satellite. Audio processing can be done at the studio, prior to transmission, unlike in 'over the air' radio (usually at the transmitter).
The main equipment at the studio is the POE (programme origination kit) and any conditioning or switching, which is normally contained in the hub's mixing desk or console. It is increasingly common to have a lot of the equipment "in the cloud" acting as a remote server. From there, audio is served as required.