Abstract: The sensor makes it possible to increase the performances, particularly from the sensitivity and frequency band standpoints, by means of a coaxial helical coil, matched to the connecting end to an auxiliary current measuring apparatus. At each turn, a portion of the external conductor is bared and equipped with elements for matching to the characteristic impedance in order to compensate the breaks caused in this way.

Abstract: Disclosed is a device for automatically controlling the gain of a receiving channel in a system comprising optical connections having a very wide pass band.The useful signal of unknown level is transmitted with a pilot signal of known level through an optical connection, where it undergoes an attenuation, to a receiving assembly connected to an opto-electronic transducer at the output of the optical channel. A device for controlling the gain of the receiving channel commanded by the pilot signal digitally controls an attenuation circuit which thereupon restores the useful signal to its initial level.