Minnesota Mining and Manufacturing Company

Peter G Burton

James K Kennedy

Telephone trunk line testing circuitry for connection to a private branch exchange (PBX) and the telephone trunk lines for the PBX including a microcomputer unit (MCU), switching circuitry, a DTMF receiver, and a tone generator for connecting one of the trunk lines as a control trunk for the circuitry. Under the control of the MCU programmed to respond to DTMF various signal commands sent from a telephone at the far end of the control trunk the circuitry operates to selectively disconnect (isolating) one of the other trunks at a time from the PBX and connect it to the circuitry with the circuitry configured under control of the MCU for completing various test involving the trunk under test (TUT), control trunk, switching circuitry and the tone generator, including the supply of tone signals from the tone generator during some of the test configurations.

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Austin, TX, United States of America

Peter G Burton