Patent ID: 6888939

Claim:
A circuit ( 1 ) for joint transmission of voice and data via a telephone line ( 2 ), having a first and a second telephone line connection (TIP, RING) for connection to the telephone line ( 2 ), having a data connection (ITD) for connection to a data line ( 3 ), having first circuit means (T 1 -T 4 , R 3 , R 4 ), which are coupled to the telephone line connections (TIP, RING) for producing a first current which is composed of the sum of transmission and received currents (Ia, Ib) which flow via the telephone line ( 2 ) and are produced via a transmission power level (Vtx) and a received power level (Vrx), respectively, and having second circuit means (T 5 , R 1 - 2 , C 1 -C 2 ) which are coupled to the telephone line connections (TIP, RING) for producing a second current (Id) which corresponds to the current produced solely by the transmission power level corresponding to the data, with the outputs of the first circuit means (T 1 -T 4 , R 3 , R 4 ) and of the second circuit means (T 5 , R 1 -R 2 , C 1 -C 2 ) being coupled to the data connection (ITD) in such a manner that a current (Ic) which is emitted via the data connection (ITD) corresponds to the difference between the first current and the second current (Id).