Black Box MD1640A User Manual

118

SERIES II INTELLIGENT DATA/FAX MODEMS

When testing is completed, you may exit Answer mode by entering
an Escape Sequence (

+++AT<CR>

<BREAK>AT<CR>

), which

returns the modem to Command mode.

Your modem passes this test if the data entered from your keyboard
is the same as the data received on your monitor. If different data is
appearing on your monitor, your modem is probably causing the
problem, although it could also be your computer. If your modem
passes this test, but you are receiving errors while On-line, the
remote modem or the phone line could be at fault.

8.3 Digital Loopback Test/V.54 Loop 2 (Local/Manual)

In this test, your modem must be On-Line with another modem that
can respond to a request for Digital Loopback, such as another Series II
Modem. The Digital Loopback Test is an on-line test that loops data
sent from one modem across the phone line to another modem, then
back to the first modem. See Figure 8-2.

There are two ways to put a modem into Digital Loopback mode.

1. Locally or Manually, described here in section 8.3.

2. Remotely or Automatically, see section 8.4.

Note:

The Digital Loopback Tests can only be used with the

modem in Normal mode (error correction off).

Figure 8-2. Digital Loopback Test (local/manual)

UUUUU
UUUUU

Computer

or Terminal

Computer

or Terminal

Local Series II

Modem

Remote Series II

Modem

Type

in Terminal mode; hit ENTER;

dial remote modem; establish On-line

mode; enter escape sequence;

type

ATU3

and hit ENTER

digital

analog

digital