General algebraic space-time code constructions are presented for Gray-mapped 2K-PSK, 2K-PAM, and 4K-QAM constellations. Disclosed is a series of improvements that make the tool lighter, more reliable and safer to operate. The pattern changes one of its characteristics as a result of an interaction with the beam. The remote module preferably includes a test signal generator configured to send test signals sequentially along each line of the cable, and includes an identifying signal generator which is configured to send an identifying signal along a line of the cable. The first to third conductive thin wires commonly includes: a first non-magnetic metal layer; a second non-magnetic metal layer; and a magnetic metal layer sandwiched between the first non-magnetic metal layer and the second non-magnetic metal layer.