公开(公告)号：DE3473803D1

公开(公告)日：1988-10-06

申请号：DE3473803

申请日：1984-06-20

Applicant: IBM ,  IBM FRANCE

Inventor： BONNET YVES AIME JEAN ,  JACQUART CHRISTIAN

IPC: H04Q3/72 ,  H04M3/22

Abstract: A constant-voltage generator comprising a 100 kHz multivibrator (30), HF transformer (28) and full-wave rectifier (D1,D2) is connected to the terminals (A,B) of a resistance (r) of 10 ohms in series with the telephone line (LL). The prim. winding of the transformer (28) is centre-tapped to a 5V DC supply via a 511-ohm resistance (R). When current flows along the line (LL), its combination with the rectified HF current is detected at the centre tap (C) and pref. compared with the reference output of another DC-DC convertor, and amplified with addn. of an AC signal (Vref) corresp. to twice the amplitude of the line current signal.