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[. . . ] ® CourierTM V. Everything Modem Command Reference http://www. 3com. com/ Part No. 1. 024. 2129-01 Published June 2000 3Com Corporation 5400 Bayfront Plaza Santa Clara, California 95052-8145 Copyright © 2000 3Com Corporation. No part of this documentation may be reproduced in any form or by any means or used to make any derivative work (such as translation, transformation, or adaptation) without written permission from 3Com Corporation. 3Com Corporation reserves the right to revise this documentation and to make changes in content from time to time without obligation on the part of 3Com Corporation to provide notification of such revision or change. [. . . ] Granting a Digital Loopback Test Request (AT&T4) Canceling All Digital Loopback Test Requests (&T5) Using AT&T4 causes the CourierV. Everything modem to grant a remote device's request for a remote digital loop-back test. Using AT&T5 cancels AT&T4, and the Courier V. Everything modem fails to acknowledge remote digital loopback test requests. This is the default so that your CourierV. Everything modem isn't subject to another user calling and tying up your Courier V. Everything modem without your permission. Testing the Courier V. Everything Modem using AT&T n 15-7 Testing Using Keyboard Data (AT&T6) 1 Send AT&M0&N3S14. 0=0 to prepare the CourierV. Everything modem for testing. This command disables error control, fixes the connection rate at 2400 bps, and makes the Courier V. Everything modem return to command mode when you type the escape code (+++). 2 Establish a connection with the remote device 3 If you haven't already done so, arrange with the remote user t cooperate with the test. If necessary, set the remote device to acknowledge the remote digital loopback request. For example, older modems need to be set to S16=8. The modem enters remote digital loopback mode, and, if the modem is an external model, the MR status light flashes. It will be looped back to your modem by the remote device and to your screen for verification. (The remote user will not see your data. ) 6 Send the escape code, +++, and the AT&T0 to end the test. Alternatively, you can end the test by sendin ATH, ATZ, or ATZ!reset the Courier V. Everything modem i addition to ending the test. If you issue an invalid command, the Courier V. Everything modem sends an ERROR message. If you set Register S18, the CourierV. Everything modem automatically ends the test when the test timeout is reached. See the example in the previous section, Stopping a Test for an example of using S18. Data errors indicate a problem with the remote device or with the phone link. 7 Send AT&M4, unless you used a reset command (ATZ or ATZ!). 15-8 CHAPTER 15: TESTING THE CONNECTION Testing Using Built-in Test Pattern (AT&T7) This test option causes the modem to perform a remote digital loopback test by sending a built-in test pattern. An internal error detector counts any errors and, when the test is ended, sends the number of errors or 00 (no errors) to the screen. However, you don't need to type anything during this test. The modem sends only its final error count to your screen 1 Send AT&M0&N3S14. 0=0 to prepare the CourierV. Everything modem for testing. This command disables error control, fixes the connection rate at 2400 bps, and makes the Courier V. Everything modem return to command mode when you type the escape code (+++). 2 Establish a connection with the remote device 3 If you haven't already done so, arrange with the remote user t cooperate with the test. If necessary, set the remote device to acknowledge the remote digital loopback request. [. . . ] Used in the U. K An ITU-T standard for modem communications. Among other things, V. 25 specifies an answer tone different from the Bell answer tone. All V. 22 V. 22 bis V. 23 V. 25 GLOSSARY 13 3Com modems can be set with the B0 command so that they use the V. 25 2100 Hz tone when answering overseas calls V. 25 bis An ITU-T standard for synchronous communications between th mainframe or host and the modem using the HDLC or character-oriented protocol. Modulation depends on the serial port rate and setting of the transmitting clock source, &X. [. . . ]