To provide dots on tape at 1/50 or 1/60 second intervals, equal to the frequency of the mains supply. Operates on12 V a.c. It has an electromagnet & a spring loaded armature which vibrates above a support table. Paper tape, drawn through guides on the table is struck by a dotting screw, carried on the armature. A peg on the table is provided to allow full use of carbon paper disc. Fitted on base.