19. A printer according to claim 18, wherein said electromagnets are of the moving coil type and comprise a common permanent magnet.
19. A printer according to claim 18, wherein said electromagnets are of the moving coil type and comprise a common permanent magnet. 26. A printer according to claim 19, wherein said tracing element includes a stylus, comprising moving means for moving the said stylus in a direction perpendicular to the paper under the control of numerical instructions, said moving means moving said stylus away from the paper when no sign is to be traced and being conditioned to vary the intensity of the printed sign by altering the pressure exerted against the paper according to said instructions.