Yip, as HavocXphere & Rockhound stated, it is a radio link for the armed response security company. Check the box close the floor, it might have a "Property of..." label since one never owns the radio link equipment & technically only have it as long as you are paying for the service. This is what the annual 'radio license fee' is supposed to cover - normally about a R100 or thereabouts.
Perhaps the previous tenants moved out before the security company could collect their equipment.