Aim of chapter I to recommend conventions on the meaning in a circuit of the positive or negative character of a current, voltage (tension), electromotive force, electric charge and magnetic flux and conventions on the methods of indicating in circuit diagrams, by gaphical symbols or by subscripts accompanying letter symbols, the sign conventions for the quantities mentioned above. Chapter II deals with conventions concerning electric and magnetic circuits under sinusoidal conditions. In a commentary more complicated examples, associating indications of the reference directions or reference polarities of several quantities in the same diagram are given.