Browse Prior Art Database

Modem Wrap Back Test

IP.com Disclosure Number: IPCOM000094271D
Original Publication Date: 1966-Aug-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Berglund, WA: AUTHOR

Abstract

In order to determine if modem transmitter and receiver 10 and 15, respectively, are functioning properly, the output of 10 is applied to 15 by closing switch SW. The output of 15 thus echoes the input information delayed by the propagation time. The maximum modem propagation time is known. If this propagation time is exceeded, an error condition exists.

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Modem Wrap Back Test

In order to determine if modem transmitter and receiver 10 and 15, respectively, are functioning properly, the output of 10 is applied to 15 by closing switch SW. The output of 15 thus echoes the input information delayed by the propagation time. The maximum modem propagation time is known. If this propagation time is exceeded, an error condition exists.

When test switch 20 is operated, test oscillator 25 provides an up level during the first half oscillator cycle and a down level during the second half. The oscillator 25 frequency is such that its half period is longer than the maximum modem delay time. The up level from 25 sets trigger 30 and is also applied to
10. Negative And 35 is conditioned during the second half period of 25. The reset output of 30 is also applied to 35.

Under proper operating conditions, 30 is reset by the output from 15 prior to the output from 25 switching to the down level. If the output from 25 is at a down level and 30 is not reset, 35 passes a signal to indicate an error condition.

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