Line transmission systems

HELECTRICITY H04Electric communication H04BTRANSMISSION

H04B3/00Line transmission systems

H04B3/02Details H04B3/03Hybrid circuits H04B3/04Control of transmission Equalising H04B3/06by the transmitted signal H04B3/08in negative-feedback path of line amplifier H04B3/10by pilot signal H04B3/11using pilot wire H04B3/12in negative-feedback path of line amplifier H04B3/14characterised by the equalising network used H04B3/141using multiequalisers H04B3/142using echo-equalisers H04B3/143using amplitude-frequency equalisers H04B3/144fixed equalizers H04B3/145variable equalisers H04B3/146using phase-frequency equalisers H04B3/147fixed equalisers H04B3/148variable equalisers H04B3/16characterised by the negative-impedance network used H04B3/18wherein the network comprises semiconductor devices H04B3/20Reducing echo effects or singing Opening or closing transmitting path Conditioning for transmission in one direction or the other H04B3/21using a set of bandfilters H04B3/23using a replica of transmitted signal in the time domain H04B3/231Echo cancellers using readout of a memory to provide the echo replica H04B3/232using phase shift, phase roll or frequency offset correction H04B3/234using double talk detection H04B3/235combined with adaptive equaliser H04B3/237using two adaptive filters H04B3/238using initial training sequence H04B3/26Improving frequency characteristic by the use of loading coils H04B3/28Reducing interference caused by currents induced in cable sheating or armouring H04B3/30Reducing interference caused by unbalance current in a normally balanced line H04B3/32Reducing cross-talk H04B3/34by systematic interconnection of lenghts of cable during laying by addition of balancing components to cable during laying H04B3/36Repeater circuits H04B3/38for signals in two different frequency ranges transmitted in opposite directions over the same transmission path H04B3/40Artificial lines Networks simulating a line of certain length H04B3/42Circuits for by-passing of ringing signals H04B3/44Arrangements for feeding power to a repeater along the transmission line H04B3/46Monitoring Testing H04B3/462Testing group delay or phase shift H04B3/466Testing attenuation in combination with at least one of group delay and phase shift H04B3/48Testing attenuation H04B3/487Testing crosstalk effects H04B3/493Testing echo effects or singing H04B3/50Systems for transmission between fixed stations via two-conductor transmission lines H04B3/52Systems for transmission between fixed stations via waveguides H04B3/54Systems for transmission via power distribution lines H04B3/542the information being in digital form H04B3/544Setting up communications; Call and signalling arrangements H04B3/546Combination of signalling, telemetering, protection H04B3/548the power on the line being DC H04B3/56Circuits for coupling, blocking, or by-passing of signals H04B3/58Repeater circuits H04B3/60Systems for communication between relatively movable stations