Patent ID: 8242632

Claim:
In combination with an electromagnetic grab normally powered from a line-voltage source having a cable with an outer end connected to the grab: a plurality of high-performance capacitors on the grab, connected in parallel, and forming an emergency power supply; a relay at the outer end of the cable on the grab, operatively connected to the line-voltage source and to the grab, and switchable between a normal position powering the grab from the line-voltage source and not from the emergency power supply and an emergency position powering the grab from the emergency power supply and not from the line voltage source; alarm means activatable for generating an alarm signal; control means connected to the relay and to the alarm means for, on detection of a current or voltage parameter of the line voltage being below a predetermined respective threshold, switching the relay into the emergency position and activating the alarm means; a transmitter connected to an inner end of the cable for continuously outputting into the cable a high-frequency signal; and a receiver on the grab at the outer end of the cable connected to the relay for operating the relay when the receiver no longer receives the signal.