| 摘要 |
<p>A ferrite loop 21 encircles the line 11 and neutral 12, but not the earth cable 13 of a mains supply. The loop 21 also encircles a further loop 22 which comprises a capacitor 23. The further loop 22 including its capacitor 23 forms a parallel LC circuit which provides a high impedance to signals at the resonant frequency of the LC circuit in a circuit including the neutral and earth cables. The filter has substantially no effect on signals at mains frequency, since the loop 21 encircles both the line cable 11 and the neutral cable 12. There is also disclosed a filtering system comprising two such filters arranged along the arm of a T-filter system, the stem of the T comprising a series LC circuit to provide a low impedance path for signals at its resonant frequency.</p> |
