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Testing Line Adapters

IP.com Disclosure Number: IPCOM000075831D
Original Publication Date: 1971-Nov-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Crooks, TL: AUTHOR [+3]

Abstract

The IBM line adapter (modem) consisting of the transmitter portion 1 and the receiver portion 2 is tested by providing space and mark signals 10 to the transmitter portion 1, which transmits them to the receiver portion 2, sampling the voltage at reference point 4, determining the period of oscillation at point 4 and comparing the oscillation period to specified limits.

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Testing Line Adapters

The IBM line adapter (modem) consisting of the transmitter portion 1 and the receiver portion 2 is tested by providing space and mark signals 10 to the transmitter portion 1, which transmits them to the receiver portion 2, sampling the voltage at reference point 4, determining the period of oscillation at point 4 and comparing the oscillation period to specified limits.

The modem is conventional. Its transmitter portion 1 comprises modulator 11, filter 12, shaping circuit 13, request to send logic 14, and line driver or terminator 15. The modem transmits variable-frequency signals on output lines 16 and, in particular, transmits mark and space signals of two different frequencies corresponding to the mark and space bits 10, applied as inputs to the modem. The receiver portion 2 comprises filter 17, clamp 18, clamp-timing logic 19, limiter 20, discriminator and detector 21, and signal delay logic 22, and takes an input signal having space and mark portions of two different frequencies and provides space and mark bits 23 as an output, corresponding to the space and mark different frequency input signals. If the modem is a two-wire unit, terminator 15 is connected directly to filter 17 to provide a direct connection between transmitter portion 1 and receiver portion 2 of the modem, but if the modem is a four-wire unit, separate input lines 16a are provided from which the input space and mark signals are derived for application to filter 17. If the modem is a four-wire unit, respective lines 16 and 16a are connected for the test.

The mark and space signals appear at reference point 4 at the...