Telephone terminal telesupply unit - is connected to telephone line and can supply current from two sources

摘要

A telesupply unit is used with telephone user terminals. It can supply current to the terminal. The unit, is connected to a symmetrical line (4) which has two current sources (1, 2) connected to the line (4). the two sources of current (1, 2) can be switched to allow transmission of the signal to the terminal. The unit has a balancing circuit connected between the two wires of the line (4). This balancing unit has two equal value resistors (R') and a transistor (30). When the current from the two sources (1,2) are different, the balancing circuit absorbs the difference.