Abstract: A railroad track segment simulator for assessing track signal susceptibility to electric power line interference including a circuit including a series dc resistor, a series inductor, and an inductive network representing characteristic impedance of an electrical R-L transmission line, resistor, inductor, and network being serially connected as a series circuit, a first ballast resistance connected between one end of series circuit and a ground potential, and a second ballast resistance connected between another end of series circuit and a ground potential. The impedance of the segment is expressed as: ##EQU1## where: f=frequency (hz),r.sub.o =effective radius of rail at power line ac frequencies=0.09 m for 132 lb/yd rail,R.sub.dc =dc resistance per kft of track,j=imaginary number,Ln=impedance per track segment.A plurality of segments can be serially connected to simulate any length of line.

Abstract: An apparatus for shielding a time dependent magnetic field comprises a magnetic metallic glass element in which a magnetic biasing field is generated having higher frequency components than the major components of the time dependent magnetic field.