Abstract: Apparatus for receiving an optical test signal, from a transmitter pulsating at a selected repetition rate, comprising, a portable voltage source, a PIN diode for sampling the test signal and generating a voltage pulsating at said repetition rate and with an amplitude proportionate to the amplitude of the sampled test signal, an indicator for indicating the amplitude of the sampled test signal, amplifying means connected between the indicator and the PIN diode, a filter circuit between the PIN diode and the amplifying means for reacting to the transitions in amplitude of said voltage from the PIN diode.

Abstract: A receiver for receiving an optical test signal from an optical transmitter pulsating at a selected repetition rate is disclosed. The receiver comprises an optical detector for sampling the test signal and generating a voltage signal pulsating at the repetition rate and with an amplitude proportional to the amplitude of the sampled test signal. The receiver also includes an indicator for indicating the amplitude of the test signal relative to the amplitude of a calibration signal.

Abstract: Method of producing a group of wires, W.sub.1, W.sub.2, W.sub.3 . . . W.sub.n, which have predetermined lengths L.sub.1, L.sub.2, L.sub.3 . . . L.sub.n respectively comprises the steps of guiding the wires from substantially endless sources of wire and locating the leading ends of the wires on a feed roll in parallel side-by-side relationship with each wire disposed between the feed roll and a separate associated pressure roll. The pressure rolls are normally spaced from the feed roll so that they are in a non-feeding position but they can be selectively moved towards the feed roll into a feeding position. The feed roll is started during each of a plurality of wire feeding cycles and during each cycle, at least one of the wires is fed by selectively moving the associated feed roll to its feeding position.