Abstract: An electromagnetic vibrator that is resonant at a frequency below one third of the frequency of an alternating current power source is driven by a linear electromagnetic motor, the airgap of which varies with the vibration of the vibrator, in which motor current flow from the power source is established during the first half cycle of the power line voltage that occurs after the airgap is a maximum, is maintained independently of the power source during at least a major portion of the next half cycle, and is reduced to zero during the next following half cycle of power source voltage. Preferably two electromagnetic motors are employed, one for each direction of relative motion between the vibrator parts.