An impulse generator includes two pairs of contacts and one indexing disk whose indexing notches are capable of moving a central resilient indexing element. The indexing element moves either toward the one or the other pair of contacts depending on the rotation of the indexing disk. Each pair of contacts is a separate contact spring assembly (15, 16; 17, 18). The indexing disk is positioned above the contact springs (15, 16; 17, 18). The indexing element is a spiral spring (10) clamped either at one or at both ends, and disposed in such a way that the centerline (14) thereof extends in relation to the indexing notches (12' and 12) so that the latter deflects the spiral spring (10) laterally toward the contact springs (15, 16; 17, 18). The spiral spring (10) is laterally deflected to actuate the respective inner contact spring (16, 17) of a contact spring assembly (15, 16; 17, 18). This results in reduced abrasive by wear of the indexing disk, and insures that a good electrical contact is reliably made.