Analog Radio Frequency Interference Filters Single pair, in-line filters designed to attenuate RFI up to -57 dB on analog lines from 75 kHz to 150 MHz. The filters require no external grounding and are balanced to 600 ohms with an off-hook insertion loss of less than 0.1 dB at 1004 Hz, thus ideal for telephony applications such as with telephones, fax machines