Abstract: The position of a rod-like article of the tobacco industry is detected by measuring the delay in receiving sound transmitted towards and reflected from the article. In a preferred arrangement a stack level detector comprises a transmitter (22) for pulsed ultrasound (above 20 kHz), a receiver (24) and a circuit (10) for measuring the delay. The circuit (10) may include a latch (30) which generates regular pulses having duration corresponding to the delay.

Abstract: Cigarette-rod weight monitoring system in which the signals from a scanner, e.g. a nucleonic device such as Molins "MODIC", are processed and stored in a memory in a digitized form, and the memory contents are used to drive an analog display device. These signals, which represent the individual cigarettes, or short lengths, are accumulated in the memory over a period which is sufficiently long for a statistically significant distribution pattern to be achieved, so that the shape of the distribution curve can be observed to determine whether it is "normal" or whether any skews or other irregularities are present. In addition the accomulated signals can be analyzed in various ways to provide quantitative measurements of overall standard deviation, or effective standard deviation either side of the mean to show whether any "skews" exist. S.D. can be calculated for whole cigarettes or short lengths for different diagnostic purposes.

Abstract: Electrical monitoring and/or control circuit including a high impedance transducer--for example a photo-diode--which is situated remotely from a measuring circuit and linked to it by a balanced twisted pair of wires fed by a power MOSFET forming a "buffer". The arrangement is such that equal pulses of opposite phase are induced in the twin feeder when a pulse output is produced by the transducer, which is substantially noise-immune without the use of coaxial cable and without the necessity for situating all the measuring circuitry at the transducer position. May be used in "difficult" electrical environments, e.g. where there are electric motors such as in tobacco-feeding arrangements.