The use of harmonised standards is optional but has the advantage of giving a 'presumption of conformity' with the essential requirements corresponding to its scope. Manufacturers may thus go for any other technical solution. If a manufacturer chooses not to follow a harmonised standard, he has the obligation to prove that his apparatus is in conformity with the essential requirements by other means and to provide a full technical justification.

欧盟最近发布了涉及通信及终端设备的200余个标准的的清单，这些标准虽然是自愿性符合标准，但是如果生产厂商没有符合这些标准的话，那他依旧有义务提供充分的证据来证明他们的产品符合必要的安全要求。