In paragraph 42 onwards of the explanatory report, this guideline is clarified as follows:

Although mechanical and electronic voting methods present clear advantages when several elections are taking place at the same time, certain precautions are needed to minimise the risk of fraud, for example by enabling the voter to check his or her vote immediately after casting it. In order to facilitate verification and a recount of votes in the event of an appeal, it may also be provided that a machine could print votes onto ballot papers; these would be placed in a sealed container where they cannot be viewed. All the methods used should enable the confidentiality of the ballot to be guaranteed (see explanatory report, §42). Electronic voting methods are “secure” if the system can withstand deliberate attack; they are “reliable” if they can function on their own, irrespective of any shortcomings in the hardware or software (§ 43). The system’s transparency must be guaranteed, in the sense that it must be possible to check that it is functioning properly (§ 43).