The disclosure relates to a method for discovery by a non-discoverable first public safety user equipment (PS UE), of a discoverable second PS UE in a public safety system comprising a telecommunications network providing a public safety spectrum for wireless access of the first PS UE and the second PS UE. The method can comprise for the first non-discoverable PS UE: transmitting synchronization information for the second PS UE; receiving at least one proximity announcement from the second PS UE in accordance with the transmitted synchronization information. The disclosure also relates to a non-discoverable public safety user device configured for performing the method, and relates to a PS server system arranged for assisting in the discovery of PS UEs.