Abstract: The invention relates to a method of purifying pyrolysis gases preferably containing hydrogen halides and/or acidic gaseous sulfur compounds by simultaneous neutralization and dust separation in which the gas entraining large amounts of dusty solid particles is led through a bulk bed for the purpose of binding the gaseous pollutants, and an apparatus for carrying out said method. The problem of clogging and plugging of the bulk bed is solved in that the grains of the bulk bed are set in shocklike movement and are thus subjected to a minimum wear by mechanical abrasion, the clogging of the bulk bed filter thus being avoided and the purification of the gas improved.

Abstract: A control system for use in conjunction with several elevators which are located close to one another and are controlled independently. The elevators are provided with a call button for each elevator door on each floor. After actuating one call button, all other call buttons on that same floor are blocked from being operative for a predetermined time interval. Each call button is constructed as a parallel contact and is connected, on the one hand, by a time relay and, on the other hand, directly to an auxiliary relay wired as an interrupter. From there, the call button is connected by a call line to associated elevator controls. The call buttons may be constructed as conventional push button switches, and a control unit in the form of a common interrupter may be installed in the call line together with a time lag relay, an auxiliary relay and an OR-circuit. The arrangement may be such that after actuating one "up" button all other "up" buttons are blocked for a predetermined time interval.