movable magnet 76 having the integrated stopper plate 78 at its front end receives a bias force in the forward direction the movable magnet 76 is normally held in position with the front end surface of the stopper plate 78 in abutment against the rear end surface of the rear yoke 64 or in alignment with the intended retracted position under the condition the remaining front end surface of the stopper plate 78 receives the rear end surface of the printing hammer 50 to keep it in home position accordingly the combined bias force applied to the movable magnet 76 in the forward direction must be sufficiently stronger than the recovery force of the spring 62 it is further to be noted that there is formed a small gap g between the stationary and movable magnets 72 and 76 when the movable magnet 76 is so located with the front end surface of the integrated stopper plate 78 abutted against the rear end surface 66 of the rear yoke 64 in front of the rear yoke 64 is disposed a spool 84 around which is provided as wound a driving solenoid 86 which in turn is energized or deenergized in accordance with a printing signal supplied from a print control circuit not shown the spool 84 together with the solenoid 86 is tightly fitted into a front yoke 88 which is generally cylindrical in shape the front yoke 88 is also tightly fitted onto the rear yoke 64 thereby.