User guide
ASCOM USER GUIDE
High Speed Base Band Modems
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5.3.2 Remote Loop
With a BERT still connected as above, turn off the local loop and apply the remote loop.
The remote loop loops data back to the user interface from the far end modem as shown
below, thus this test can be used to check the integrity of the line.
There should be no errors or a very low error rate. If the error rate received is too high for your
application, try a lower data rate. When you have completed this test, turn off remote loop.
If a BERT is not available then the test can be carried out by using the in-built data test.
For details on how to do this see section 6.6.5.
5.3.3 Far End Local Loop
If the two tests above have been performed then also perform test 5.3.1 (local loop) on the
far end modem. This can only be performed when the far end modem is local to the operator.
Interface
Transmission
System
Interface
BERT
remote loop selected from this modemloop applied here
Transmission
System
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22 ASCOM USER GUIDE
High Speed Base Band Modems
5.2 DEFAULT CONFIGURATION
The modem has a default configuration, and reverts to this when:
(1) The interface module has been changed.
(2) The stored configuration has become corrupted. This could occur if power was lost when
the configuration was being stored.
The modems signify the use of the default configuration by turning the program LED on after
the unit has powered up.
The default configuration is:
Modem mode: Slave
Number of line pairs: 1
Line rate: 64k
Internal / external timing: Line Clock
Interface control: Controls EOC
Transmit power: Auto
In the interface menus:
All clamps OFF, except, for V.35, V.36, and RS530 only:
Circuit 108 Set On
5.3 LINK PERFORMANCE
The high-speed modem has a number of features to aid in the testing of the data link.
To check a data link the following tests can be performed. Some of the tests outlined will
require the use of a Bit Error Rate Tester (BERT).
5.3.1 Local Loop
With a BERT connected to the user interface a local loop will loop data back to the user
interface as shown below. If everything is ok, no errors should be detected i.e. the user
interface is correctly transporting data.
Interface
Interface
Transmission
System
BERT
local loop applied in this modem
Transmission
System