Abstract: A braking device is arranged around a piston of a hydraulic elevator drive and serves for locking of the piston carrying an elevator car or a cable pulley by engaging at least two brake arms, each rotatable around axes. The brake arms are actuated by a brake drive having a brake cylinder with a plunger biased by hydraulic fluid to release the brake arms. In response to a pressure drop in the brake cylinder, or at an unauthorized downward motion of the elevator drive piston, the brake arms are closed by the brake drive and the elevator drive piston is prevented from moving. A brake control circuit connected to a power supply actuates the brake drive and includes a buffer battery backup in case of failure of the power supply and a storage capacitor backup in case of failure of the battery.