Abstract: A light scanning system for needles in knitting machines, more particularly circular knitting machines, with a control unit, which comprises at least a light source and an evaluating unit with a receiver, at least a first (22, 42) and a second (24, 44) light wave conductor, the first light wave conductor (22, 42) having a first end, which is connected to the light source in order to supply light into the first light wave conductor, and having a second end (26), which is secured in a casing (20, 46) for transmitting the light to a needle, and the second light wave conductor (24, 44) having a first end (30), which is secured in the casing (20, 48) so close to the second end (26) of the first light wave conductor (22, 42) that radiation reflected by the needle enters the second light wave conductor (24, 44), and having a second end, which is connected to the evaluating unit, so that the reflected radiation is supplied to the receiver.

Abstract: A device for the photoelectric supervision of a warp loom for irregularities in the yarn supply of a yarn sheet has an infrared radiation source and receiver, which are arranged so that the infrared beam is alternately interrupted and released, in time with the frequency of the oscillating eye needles, by the needles as well as by the yarns passing therethrough. This periodic supervisory signal sequence is periodically processed by a gating circuit only during a preset gating time period (T.sub.X) within each beam release phase (T.sub.p). The signal values issued in each window pulse gating phase are compared in a comparator circuit with a comparison value. If the latter is not attained, a control signal is generated for the warp loom.