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Charles Industries, LLC
An Amphenol Company

1450 American Lane
20th Floor
Schaumburg, IL
60173-5492 USA



Severe Service RFI Suppression Networks provide dual performance suppression to minimize interference in voice frequency loops

Radio Frequency Interference (RFI) occurs when a source of RF emission is located very close to a cable plant or where adequate shielding and bonding of the telephone facilities is not feasible, such as near or at the customer premises.

Unwanted RF energy can be picked up by the cable plant, which acts as an antenna. These unwanted signals are demodulated to voice frequency and carried directly to the telephone set.

Both metallic and longitudinal RF interference are attenuated by Charles high performance Severe Service RFI Suppression Networks.

  • Metallic noise enters the network on one side of the pair with return path provided by the other side of the pair
  • Longitudinal noise enters the network on either one or both sides of the pair; ground is the return path

Severe Service RFI Suppression Networks


Model 12-14C allows the "notch" (or peak attenuation) of at least - 68 dB to be varied by 1120 KHz in eight user-selected steps. Eight DIP switches allow the attenuation notch to be closely turned to the known center frequency of the identified unwanted RF emission.

Model 12-15D provides superior broadband attenuation of -90 dB at 1000 KHz in cases where the center frequency of the RF emissions cannot be identified or there are multiple RF sources. This UL listed product eliminates the need for expensive and time-consuming signal tracking equipment.

Audible RF noise may also be created within the telephone set. Circuits and certain components within a telephone set can act as both antenna and receiver (demodular) for RF emissions from a nearby source. Maximum performance of any RFI suppression network can not be assured in such situations.


Model 12-14C Model 12-15D
Insertion Loss at 104 Hz 0.2 dB 0.5 dB
Critical Frequency 700-1820 KHz 830 KHz
Attenuation Distortion
(200 to 3400 Hz)
0.1 dB 0.1 dB

Ordering Information

12-14C Water-resistant housing
Spade leads that mount virtually anywhere
Band selector switch tunes filter to specific RFI frequency
Spade terminals and turning chart is included
12-15D Water-resistant housing
Spade leads
Can be installed in any convenient location
Inside plant wiring complies with Underwriter’s Laboratories Standard 1459, 2nd Ed.

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