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Provide dual performance suppression to effectively minimize interference in voice frequency loops

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

Generally, this unwanted RF energy is caused by an AM broadcast band radio station. The RF energy is picked up by the cable plant, which acts as an antenna. The unwanted signals are demodulated to voice frequency and carried directly to the telephone set.

Metallic noise enters the network on one side of the pair with the 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. Both metallic and longitudinal RF interference are attenuated by these UL listed networks.

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 (demodulator) for RF emissions from a nearby source. Maximum performance of any RFI suppression network can not be assured in such situations.

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Typical Attenuation Curve

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RFI Suppression Networks 12-11C, 12-12C and 12-13C complies with Underwriter’s Laboratories® Standard 1459, Second Edition. Compliance is restricted to inside plant wiring


Insertion Loss dB at 1004 Hz 0.3
Critical Frequency - KHz 710
Attenuation Distortion
(200 to 3400 Hz)
0.1 dB

Ordering Information

12-11C Mounted on1/2 ringer board that can be installed in various network interface devices, modular surface jacks or telephone jacks.
Spade terminals included.
12-12C Encased in water-resistant housing with spade leads.
Can be installed virtually anywhere.
12-13C Encased in water-resistant housing with modular male lead and female RJ-11 for modular terminations.

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