| 摘要 |
<p>A transformer (44) for coupling analog information and a switch (50) responsive to a hook condition signal (51) are provided. The hook condition signal (51) provides an indication of the "on/off hook" condition of a corresponding telephone subscriber. The switch (50) provides a closed circuit condition to "sink" a DC current when the corresponding telephone subscriber is "off hook" and an open circuit condition when the corresponding subscriber is "on hook". The telephone interface circuit (70) further includes a capacitor (47) serially coupled with the primary winding (45,46) of the transformer (44), to prevent DC current from passing through the primary winding (45,46) of the transformer (44). The telephone interface circuit (70) can be adapted for use as a remote terminal interface circuit or as a central office terminal interface circuit. The interface circuit (70) includes first and second circuit paths (77,78) disposed in parallel with each other. The first circuit path (77) includes the transformer (44), switch (50), and capacitor (47) as described above. The second circuit path (78) includes a subscriber line interface circuit (39). The interface circuit includes jumper wires (79a-79h) for selectively coupling either the first circuit path (77) or the second circuit (78) path between a first pair of terminals (71,72) and a second pair of terminals (75,76) of the interface circuit (70). <IMAGE></p> |
