Black Box MD1641A Manuale Utente

In this test the local modem is placed in Digital Loopback mode. Data 
is entered and transmitted from the remote modem (which is not in
digital loopback mode), sent across the phone line to the local modem
and looped back to the remote modem. 

The test procedure is as follows: 

1. 

Go into Terminal mode. Type

and hit ENTER; you should get

an OK message. 

2.

Dial the remote modem by entering the Dial command and the
phone number, to establish On-line mode. 

3.

Type the Escape Sequence (

or 

)

which brings your modem into Command mode, while still main-
taining the pseudo On-line mode with the remote modem. 

4.

Type 

from the local PC and hit ENTER. Once you receive an

OK message from your modem (if responses are enabled), the local
modem is placed in Digital Loopback mode.

5.

Data is typed from the remote keyboard. For this test, typing
multiple upper case "U" characters is a good way to send an alter-
nating test pattern of ones and zeros. The data received by the local
modem will enter its analog receiver, be converted to digital data,
be reconverted into analog, and then looped through its
transmitter back to the remote modem. Your modem passes this
test if the data entered from the remote keyboard is the same as 
the data received on the remote monitor. 

6.

When testing is complete, you may end the test by typing an Escape
Sequence (

or 

) to bring your

modem into Command mode. The modem should respond with
an OK message. If you wish to stay On-line with the remote modem
for normal data transmission, type 

and hit ENTER. If you wish

to terminate the call, type 

and hit ENTER to hang up.