A wireless signal transmitter is provided for a radiotherapy device, said radiotherapy device being configured to provide radiation to a subject via a source of radiation, and further being configured to output a non-continuous beam of radiation, wherein said non-continuous beam of radiation has a first, time-related property associated therewith. The wireless signal transmitter is configured to wirelessly transmit a signal comprising data regarding the first, time-related property that is associated with the non-continuous beam of radiation, to a wireless signal receiver.