Abstract: An adsorbent is described based on an inorganic support material with exchangeable mono- and divalent cations, characterized by the fact that the specific surface of the support material is >100 m.sup.2 /g, its cation exchange capacity is>30 mg-equiv/100 g, its pore volume is>0.15 m/g, the pH value of an aqueous suspension of 8 g of support material in 100 mL of H.sub.2 O is<7.5 and that at least 60, preferably at least 70% of the exchangeable mono- and/or divalent cations are exchanged by cations acting as Lewis acids, preferably Al.sup.3 + cations.

Abstract: A process is described for activation of layered silicates having an ion exchange capacity (IEC) of at least 25 meq/g by treating them with an acid, characterized in that the layered silicate is activated with about 1 to 10% by weight (based on the dry layered silicate) of an acid at a temperature of not more than 80.degree. C. and the activated layered silicate is calcined at temperatures of about 200.degree. to 400.degree. C. and comminuted desired.

Abstract: The polarity of the desired speed voltage of a speed control device and the commutation sequence of the current flowing in the stator windings are reversed for reversing an electronically commutated D.C. motor. A voltage, proportional to the EMF ad obtained from the motor voltage by I.times.R compensation, is used as the actual speed voltage for the speed control device, the polarity of the voltage proportional to the EMF being reversed when the direction of rotation signal changes.

Abstract: In a control signal transmitter for the commutating device of an electronically commutated motor, which contains at least two rotor position transmitters, particularly Hall effect generators, and an evaluation circuit which derives control signals for the commutating device from the output signals of the rotor position transmitters which determine the individual switching instants for the switching elements of the commutating device, in order to permit operation with a higher number of pulses, the evaluation circuit also includes a logic circuit to which the output signals of the rotor position transmitters are fed which circuit furnishes further control signals for the commutating device.

Abstract: An error correcting typewriter wherein a backspace correction key is operative to read an incorrect character from memory, to in turn reversely move a stepper motor controlled carriage twice the width of a character in error and then forwardly the width of the character in error and then to effect overstrike printing of the character in error.

Abstract: The control signal generator contains two Hall effect generators which are shifted relative to each other by 90.degree. electrically and magnetically, alao a gating circuit which derives from the Hall signals control signals for the switching elements of the commutating device. In order to make it possible to drive the motor digitally, the invention provides that the gating circuit comprise a combinatorial circit and, succeeding it, a 1-of-4 logic circuit. The combinatorial circuit furnishes two digital drive signals whose switching instants are shifted correspondingly .+-.45.degree. electrically relative to the zero crossings of the Hall signals.