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Selecting Test Features
Using DS1 LOOP Codes
Using DS1 LOOP Codes
Description
A loopback code causes the far end equipment to return a signal to the sender, so
that the sender can verify signal integrity. Loop codes are used by carriers of the T1
signal and users of the transport medium as a maintenance tool to aid in fault
location. Loopback commands are in-band (that is they use the payload space), and
out-band (they use an ESF data link).
The OmniBER 718 provides both In-band and Out-band loop codes as follows:
Out-band Loop
Out-band codes are transmitted in an ESF data link, in addition to transmitting the
Codes
in-band signal in the payload. They are only available when ESF framing is selected
on the Transmitter Output
Note that when switching from an idle message to a loop-back message, the loop-
back message will start following the idle message and not part way through it.
Note that the left most bit is transmitted first, and that when a loop code is not being
sent, the idle data link sequence is sent. This is a continuous repetition of the pattern
01111110
In-band Loop
With in-band codes, the transmitted signal comprises the entire payload of the signal,
overwriting whatever signal was there before. The signal may be framed or
Codes
unframed. When framed the framing bits overwrite the loopback code (see "In-Band
DS1 Loopcode 156MTS Compatibility" on next page).
Note the user word can be set to any length, between 3 and 8 bits. The left most bit is
transmitted first.
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MAIN SETTINGS
Loop type
Activate
Line
11111111 01110000
Payload
11111111 00101111
Network
11111111 01001000
Universal
n/a
User Code
page.
Deactivate
1111111100011100
11111111 01001100
n/a
11111111 00100100
111111110xxxxxx0
105
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