Interference limiting two-port network for 1+1 type transmission systems

An interference-limiting two-port network for use in a 1+1 type transmission system connecting two subscriber terminals via a common two-wire link to a telephone exchange provided with an exchange battery, one of the subscriber terminals being connected via a channel referred to as an audio channel using base band transmission over the common two-wire link and being remotely powered by the exchange battery via said two-wire link, the other subscriber terminal being connected via a channel refered to as a super-audio channel using frequency transposed bands for transmission over the common two-wire link, the audio and super-audio channels being superimposed on the common two-wire link and being separated at the ends of said link by separation filters, each of which includes a low pass filter connecting the common two-wire link to a two-wire line on which the audio channel is isolated, wherein said interference-limiting two-port network is located at the exchange end of the system and comprises two current limiter circuits, each placed in series in a respective one of the two wires of the two-wire line of the audio channel in between the low pass filter of the exchange end separation filter and the rest of the exchange.