Subscriber Line Interface Circuit
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-01
The figure illustrates the subscriber line interface (SLIC) which has the function of providing power to a variety of types of telephone sets without regard for their voltage requirements, and while minimizing the amount of injected noise from the power supplying the SLIC circuit. Conventional telephone handsets include a microphone which has a carbon canister filled with granules of carbon. In the conventional mode of operation, the carbon canister has a DC voltage applied across two plates, and the energy supplied by a spoken voice signal mechanically oscillates the granules so as to change the effective resistivity of the canister between the electrical plates. In order to make the carbon canister-type microphone work, a source of DC current must be supplied.