Abstract: A mechanically operating pendulum clock is provided with an electronic cocting device which comprises a quartz oscillator. An electronic frequency divider generates from the oscillation frequency of the quartz oscillator a frequency equal to that of the pendulum. A permanent magnet is arranged on the pendulum to cooperate with a control coil forming an electro-mechanical converter. The control coil is effective at least in the two turning positions of the pendulum. A contact-free pendulum sensor is also provided. A proportional electronic control device includes a converter which produces rectangular signals from the signals emitted by the quartz oscillator and the sensor, and a comparator is adapted, depending upon the reciprocal phase position of the quartz oscillator and sensor signals to transmit delay or acceleration signals to the control coil as well as opposing acceleration or delay signals to the control coil but phase-shifted by 180.degree..