Circuit arrangement for DC-feeding of a telephone line.

摘要

The circuitry supplies a constant DC voltage to a telephone line (a,b). An a-d converter (4) digitises the current (i) flowing on one of the lines (a) and supplies this to a digital low-pass filter (5,6). A digital current voltage converter (10) is connected to the low-pass filter (5,6). A further digital low-pass filter (11,8) is connected to the current voltage converter (10). A d-a converter (12) converts the digital value from the further filter (11,8) into a voltage (U) and supplies the other telephone line (b). Circuitry (7) associated with at least one of the filters (5,6) has a predetermined start time to reduce the rise time of the filter.