required in the prior art for assuring the constant characteristics for release and travel on the needle by supplying the electromagnet with a constant energy amount in spite of voltage changes this is also unnecessary for preventing the needle from being damaged accordingly it is unnecessary to provide a constant energy compensating circuit which makes the time for energizing the coil vary in proportion to 1 change in voltage 2 with the mechanical assist as shown in fig5 work normally performed inefficiently by the electromagnet is replaced with work more efficiently performed by the rotating cams in this way the advantages described above are achieved an alternative embodiment of a printer using a mechanically assisted electromagnet and having only one rotating cam is described with reference to fig7 the electromagnet 1 5 7 pivoted attractable plate 51 with an engaging portion 52 and springs 53 54 are similar to the corresponding elements in fig5 a hammer 65 is shown in this construction fig7 although it should be understood that either a hammer or a needle is equally applicable with the electromagnet constructions of fig5 and 7 a cam 81 rotates to deflect a spring 82 which is engaged in a recess in the hammer 65 projections 66 67 extend from the hammer 65 and guides 60 61 62 serve to align the hammer 65 for travel toward the character ring 24 having raised characters 25 on its periphery when the cam 81 rotates as indicated by the arrow the hammer 65 returns to a standby position away from the character ring 24 as the cam 81 pushes against the spring 82 as the hammer 65 moves away.