Patent ID: 7706526

Claim:
Apparatus for deriving power from a twisted pair of telephone lines for powering an auxiliary electrical device, comprising: a power supply having first and second terminals for connection to said twisted pair at an intermediate location between a central office and a customer premises, the power supply receiving on said first terminal an input voltage and input current from a first line of said twisted pair and converting said input voltage and input current to a preselected output voltage and output current for powering said auxiliary electrical device, the second terminal of the power supply providing a return current to a second line of said twisted pair, the power supply having a first current regulator at an output thereof for limiting said output current to a first predetermined value less than an off hook current in said twisted pair; and a second current regulator adapted to be disposed in the second line of said twisted pair at said intermediate location for receiving current from the customer premises flowing in the second line to the central office, the second current regulator further receiving said return current from the second terminal of said power supply, and the second current regulator being responsive to the total current flowing in the second line to the central office corresponding to the combination of said current from said customer premises and said return current from said power supply for limiting the current from the customer premises such that the total current flowing in the second line is less than a second predetermined value during an off hook condition at the customer premises.