Abstract: An apparatus for converting a mechanical force into an electrical signal. The apparatus includes a piezoelectric disk crystal (1), connecting electrode layers (2, 3) disposed on opposite sides of the disk-shaped crystal (1), the electrode layer (3) on the one side being divided into a transmitter electrode layer (6) and a ground or o-electrode layer (5), and the electrode layer (2) on the opposite side being divided into a receiver electrode layer (7) and a ground or o-electrode layer (8).

Abstract: An apparatus for monitoring one or more threads in a sewing machine with a number of sewing heads, the signal emitter including a spring arm (2) which is fixedly anchored at its one end (3) and, at its opposite end, carries a magnet (9), this opposite end being moreover located in the path of movement of the lower thread (12) in order to be influenced by same and thereby change the position of the magnet (9) in relation to an element (10) sensitive to the position of the magnet (9) and generating an electric signal in dependence upon the position of the magnet (9), the signal change being sensed and evaluated.

Abstract: The disclosure relates to an apparatus for controlling a number of boilers which are, in terms of water engineering, interconnected in series and each are provided with their control equipment having a first and a second switch, the first switch being arranged to generate a signal "permission to increase", and the second switch being arranged to generate a signal "permission to reduce", whereby the boilers are given priority ranking in such a manner that the first boiler must always attain full output before a subsequent boiler can commence to be connected in and so that a subsequent boiler must always be reduced to zero output before a preceding boiler can commence to reduce its output.

Abstract: A device for indicating the triggering of a signal transducer in, for example, thread surveillance and monitoring systems.