Importance

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Abstract

A telephone line circuit for supplying energizing current to a telephone line and for providing a voice frequency connection between the telephone line and an associated switching facility includes a transformer having a split primary winding, consisting of n turns, for connection across the telephone line and for connection to a power supply or battery. A first current flows in the split primary winding in proportion to the telephone line load characteristic. A balance winding in the transformer is connected in series with one portion of the split primary winding. The balance winding is counter-wound relative to the split primary winding and consists of more than n turns. A circuit including a current regulator causes sufficient balance current to flow in the balance winding to substantially cancel the d-c flux associated with direct current in the split primary winding. The first and balance currents additively combine to produce the energizing current for the telephone line, whereby the load on the power supply is no greater than that of a conventional line circuit in spite of the balance current requirement.

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First Claim