This specification applies to fixed capacitors and resistor-capacitor combinations for electromagnetic interference suppression (formerly called radio interference suppression) for use within, or associated with, electronic or electrical apparatus and machines where the capacitors will be connected to a main supply with a voltage not exceeding 500 V d.c. or 500 V a.c. (r.m.s.) between conductors or 250 V d.c. or 250 V a.c. (r.m.s.) between any one conductor and earth and with a frequency not exceeding 100 Hz.