3Com 56K manual Digital Loopback Testing AT&T3, Remote Digital Loopback Testing AT&T6, AT&T7

	Digital Loopback Testing (AT&T3)	14-5
	Remote Digital Loopback Testing (AT&T6, AT&T7)	14-6
	Granting a Digital Loopback Test Request (AT&T4)	14-6
	Canceling All Digital Loopback Test Requests (&T5)	14-6
	Testing Using Keyboard Data (AT&T6)	14-7
	Testing Using a Built-in Test Pattern (AT&T7)	14-8
	Testing the Business Modem using S-Resister 16	14-9
	Analog Loopback (AL) S16=1D	14-9
	Testing Using Keyboard Data (ATS16=8)	14-10
	Testing Using a Built-in Test Pattern (ATS16=4)	14-11
	Ending Testing That Uses the Test Pattern	14-11
15 TROUBLESHOOTING
	Problems That Occur Before Connecting	15-1
	No response to AT	15-1
	The Business Modem won't dial	15-2
	Double characters are appearing on your monitor	15-3

After you dial, the Business Modem reports NO CARRIER and then hangs up

15-3
Hear ringing but the Business Modem won't answer	15-3

The Business Modem acts as though a data link has been established, but no call was received, ..................................................................15-3

The Business Modem behaves as if <Enter> were pressed when you don't

press any keys	15-3
Problems that Occur After Connecting	15-4
Your screen displays random or "garbage" characters	15-4
Many CRC errors	15-4
Mainframe computer keeps dropping your connection	15-5
Bad faxes or can't fax	15-5
Both devices exchange carrier signals, but fail to establish a
communications link	15-5
Errors during software download	15-6
If You Still Have Problems	15-6

16UPGRADING YOUR MODEM

Overview	16-1
Checking Your Business Modem’s Software Version	16-1