A method of pairing a therapeutic product delivery device to a handset is described. The handset is restricted to controlling only delivery devices which it is paired with. The method comprises the steps of: at the delivery device, setting, in response to the delivery device being connected to a charging device, a pairing indicator indicating that the delivery device is available for pairing, and broadcasting the pairing indicator using a radio transceiver； at the handset, discovering the delivery device based on the broadcast pairing indicator； and pairing the discovered delivery device and the handset together. By limiting the handset to pairing with devices which are broadcasting a pairing indicator, and by limiting the setting and/or broadcast of the pairing indicator to when the delivery device is connected to a charging device, the risk of accidentally pairing the wrong delivery device (for example someone else's) to the handset is greatly reduced.
