ALARM AND TEST SYSTEM FOR A DIGITAL MAIN LINE

摘要

A test system directed to apparatus for transmitting and receiving multiple telephone transmission signals over a single twisted pair (100). The system converts an analog signal from a local switching (112) station to an 80 ksymbols/sec signal for transmission over a twisted pair by a line card (104). A remote terminal (10 2) converts the 80 ksymbols/sec signal back into a con- ventional analog signal for use in conventional telephone (108), facsimile o r other related equipment. The test equipment separ- ately tests the entire system, the tine card portion of the system, the remo te terminal portion of the system, and the twisted pair. An improved 2-to-4-wire hybrid coupling circuit (202) also is disclosed. The improved circuit has 2 extra "wing" coils attached to the known output transformer, the added coils improving the signal strength of the received signal as well as effectively cancelling out feedback from the output amplifier.