×

Method of providing d.c. feed to a telephone line

  • US 5,511,118 A
  • Filed: 04/21/1995
  • Issued: 04/23/1996
  • Est. Priority Date: 01/31/1991
  • Status: Expired due to Term
First Claim
Patent Images

1. A method of providing d.c. feed to a two-wire telephone line, comprising the steps of:

  • generating a supply voltage for a drive circuit including two amplifiers each having an output coupled to a respective wire of the line;

    supplying an a.c. transmission signal to the line via the amplifiers of the drive circuit;

    determining potentials at the amplifier outputs in dependence upon the supply voltage and headroom voltages required for operation of the amplifiers to supply the transmission signal to the line, a difference between the potentials at the outputs of the two amplifiers producing a loop current on the line;

    monitoring the loop current on the line; and

    digitally controlling the generated supply voltage in dependence upon the monitored loop current by the steps of, iteratively at each of a plurality of successive time instants;

    determining a target value corresponding to a target voltage inversely dependent upon an amount by which the monitored loop current exceeds a predetermined value; and

    adjusting the generated supply voltage towards the target voltage in dependence upon the target value;

    whereby the target voltage and the generated supply voltage converge over said plurality of successive time instants.

View all claims
  • 5 Assignments
Timeline View
Assignment View
    ×
    ×