Patent ID: 8787539

Claim:
A coupling device of a DC power supply line to a telephone line or coaxial cable, said coupling device having a first connection pad to a DC power supply line and a second connection pad to a telephone line or coaxial cable adapted to provide a DC voltage and a DC supply current to at least a telecommunication device connected thereto, said coupling device having an electrical path, defined between said first pad and said second pad, adapted to be crossed by said DC supply current, at least an AC blocking transistor inserted in said electrical path, having a first current terminal functionally coupled to said first pad and a second current terminal functionally coupled to said second pad; a control circuit connected between said second current terminal and a control terminal of said AC blocking transistor, adapted to generate a DC control voltage of the AC blocking transistor to keep it in a linear functioning condition at the edge of a saturation functioning condition when the DC supply current flows through the AC blocking transistor, wherein said control circuit is a low-pass filter adapted to generate said control voltage as a low-pass replica of the voltage on said second current terminal.