INTERFACE MODULE FOR TELEPHONE LINES

摘要

A monolithic module acting as the interface between a modem and leased ("LL") or switched ("SL") telephone lines, mainly characterized in that: 1. It can be formed on a silicon chip (due to the absence of electromechanical relays or similar switching means), and 2. Its architecture is such that it makes it possible, by interconnecting or "stacking" identical modules, not only to attach additional telephone lines, but also to increase the number of allowable modem configurations. The module (10, 10') comprises two controlled-type line amplifiers (DLL, DSL) which exhibit a high output impedance regardless of whether the power supplies are "on" or "off"; two controlled-type line receivers (RSL, RLL) which provide a very high input impedance whether the power supplies are "on" or "off"; and a wrap receiver (WRP) for testing the modem (to the exclusion of the telephone lines) and interconnecting or "stacking" identical modules. The figure shows an embodiment wherein two of the modules are interconnected; various configurations can be obtained depending on the logic state of the control inputs (1 to 4 for module 10 and 1' to 4' for module 10') supplied by the modem.