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Remote Loop Test for Multiport Modems

IP.com Disclosure Number: IPCOM000048204D
Original Publication Date: 1981-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Cholat-Namy, J: AUTHOR

Abstract

The figure illustrates local and remote multiport modems communicating across a transmission channel. A remote loop test technique is described that allows the satisfactory working of the multiplex/demultiplex apparatus in the remote modem to be checked.

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Remote Loop Test for Multiport Modems

The figure illustrates local and remote multiport modems communicating across a transmission channel. A remote loop test technique is described that allows the satisfactory working of the multiplex/demultiplex apparatus in the remote modem to be checked.

The local modem interfaces with four ports of a central processing unit (CPU), and the remote modem interfaces with four ports of data terminal equipment (not shown). The local modem multiplexes the four data channels Ax, Bx, Cx, and Dx into a single bit stream for transmission over line 1 to the remote modem, which demultiplexes the received bit stream into data channels A'r, B'r, C'r, and D'r. The remote modem multiplexes the four data channels A'x, B'x, C'x, and D'x into a multiplexed signal for transmission over line 2 to the local modem, which demultiplexes the received signal into data channels Ar, Br, Cr, and Dr.

The test sequence is initiated by the CPU which transmits a special test command on channel Ax to the local modem. The latter recognized the command, transmits a wrap command to the remote modem and switches the multiplex/demultiplex apparatus MPX/DPX 1 to the "only channel (Ax, Ar)" channel configuration. The remote modem accepts the wrap command and loops data channels A'r, B'r, C'r, and D'r back to channels A'x, B'x, C'x, and D'x, respectively.

The CPU transmits a test pattern to the local modem transmitter via Ax, MPX/DPX 1 and Transmit Data lead TD1. The...