Steel Ribbon Interrupter.
For light currents and rapid vibrations, such as are employed in electrotherapy, the steel ribbon interrupter is suitable. It consists of a steel ribbon V one-half inch wide by six or eight inches long and the thickness of a stout visiting-card. Near the end is riveted a platinum contact. One end of the ribbon is held by a brass upright R, to which connection is made to circuit; the other end is riveted to a threaded rod, which passes through a brass pillar, and is held by a thumb-screw and check nut S. Turning the thumb-screw either way tightens or loosens the ribbon and so raises or lowers the rate of vibration (Fig. 24).
Contact Breakers in Vacuo.
Contact breakers in vacuo, as applied to Ruhmkorff coils, are by no means of recent date. Poggendorff made use of such prior to 1859, and noted the diminished sparking at the contact breaker and increased effect in the secondary circuit.
Fig. 24.
Fig. 25.