Abstract: A Radio Frequency Interference Filter (10, 12) is connectable in series in the tip (T) and ring (R) branches of a telephone circuit. A first suppression stage (20) has a first inductor (L1) connectable to the tip (T) branch of the circuit and a second inductor (L2) connectable to the ring (R) branch of the circuit. The second suppression stage (22) of one embodiment of the filter (10) has a transformer (T1) with one winding (W1) connected in series with the first inductor (L1) for the tip (T) branch of circuitry and the second winding (W2) connected in series with the second inductor (L2) for the ring (R) branch of circuitry. In a second, alternative embodiment of the filter 12, the second suppression stage (22) has one ferrite-core inductor (L3) connected in series with the first inductor (L1) for the tip (T) branch of circuitry and a second ferrite-core inductor (L4) connected in series with the second inductor (L2) for the ring (R) branch of circuitry.

Abstract: A modular signal attenuator is provided by resistors (R1, R2 and R3, R4) connected in respective series for connection in each branch of tip and ring telephone circuitry. A pair of capacitors (C1, C2) connected to equate to a non-polar capacitor and a resistor (R5) connected in series are shunted across the serially-connected resistors (R1, R2 and R3, R4) between adjacent resistors (R1 and R2, R3 and R4) of each series of resistors in the tip and ring branches.