interrupted this relay is de energised so that after a short time the relay 86 becomes excited and changes over its switch contact 94 now the terminals 20 of all electric motors are applied to the positive pole of the voltage source via the switch contact 94 the collecting main 54 and the bridging contact 33 of the assigned reversing switch 30 the terminals 11 of all motors is connected to earth via the bridging contact 14 of the position switch 13 and the bridging contact 31 of the reversing switch 30 the motors therefore reverse their direction of rotation so that all doors are locked the current relay however cannot be excited because it is short circuited via the switch contact 95 of the relay 86 in the circuit arrangement according to fig2 the electric connections within the motor unit 19 and within the reversing switch 30 and the interconnections between these to units and the connections to other components are completely the same as in fig1 but in the control device the two relays 85 and 88 are omitted the input 64 is directly connected to the output 60 and the input 66 is connected to the output 60 via the current relay 87 and perhaps via the switch contact 95 of the relay 86 connected in parallel to.