GB1461483A - Attenuation-correcting systems - Google Patents

Abstract

1461483 Line equalizers SIEMENS AG 21 March 1974 [11 April 1973] 12702/74 Heading H4R An equalizer particularly for cables in a pcm transmission system, includes at least one controllable correcting stage providing frequency dependent amplification and including an active transistor amplifier stage provided with a series resonant circuit in series with a controllable impedence element, or a parallel resonant circuit in parallel with a controllable impedence element, the controllable element being controlled by the output of an integrating amplitude controller driven from the system output. In a preferred embodiment Fig. 5 each controllable correcting stage 1 and 2 comprises a grounded emitter transistor stage having a series resonant circuit providing emitter feedback with the controllable impedance provided by an f.e.t. 17 whose gate is fed with the output of the integrating amplitude controller 3. An additional gain controlled frequency independent amplifier 5 is connected between the correcting stage 2 and the output with common control of all the controlled stages. Alternative correcting stages have parallel resonant circuit in the collector circuit of a grounded emitter stage, Fig. 8 (not shown) or parallel resonant circuits in the feed-back path of an operational amplifier Fig. 9 (not shown) or a series resonant circuit in the input of an operational amplifier, Fig. 10 (not shown). A fixed frequency dependent correction circuit can be arranged to be switched into or out of circuit at the input to the controllable stages to vary the range of correction available Fig. 7 (not shown).