single file of rod shaped articles which are formed by the cutoff of a cigarette or filter rod making machine is monitored by an apparatus having two spaced apart air discharging nozzles one of which is located upstream and the other of which is located downstream of the accelerating cam which propels successive articles of the file into successive flutes of a row forming drum at least one of the nozzles is sealed by an article when the machine produces a continuous file of articles if both nozzles can discharge air at the same time the pressure in a conduit which communicates with the nozzles decreases and such drop in pressure is detected by a diaphragm transducer or by the cylinder and piston unit of a pneumatic bridge circuit this results in the generation of a signal which is used to arrest the prime mover of the machine application_number US 69584376 A description fig1 shows a cigarette making machine of the type known as garant trademark produced by hauni werke korber amp co kg hamburg federal republic germany the machine comprises a distributor d which is mounted in or on a machine frame f and causes a wide shower of tobacco particles to descend into an elongated channel 1 onto the upper reach.