
Configuring HSSI Services
117345-B Rev. 00
5-9
Setting Up DTE Loopback Testing
On ASN and System 5000 platforms, the DTE loopback diagnostic function
provides loopback testing to the DCE. When the DTE (router) transmits a
loopback signal to the DCE, the DTE waits for the DCE to acknowledge and
return the signal. The DCE provides the transmit and receive clock signals over a
full-duplex DTE-to-DCE connection. The DCE provides the transmit and receive
clock signals.
There are four DTE loopback settings:
• No_Loopback -- Prevents the DTE from sending loopback signals to the
DCE.
• Local_Digital (Loop A) -- Allows the DTE to check the DTE/DCE interface.
In a Loop A test, the DTE transmission is returned to the DTE on the received
local DCE data circuit. The CA LED (DCE Ready) must be on.
• Local_Line (Loop B) -- Allows the DTE to check the DTE/DCE interface and
the transmit and receive sections of the local DCE. In a Loop B test, the output
of the transmitting section of the DCE is returned to the receiving section of
the DCE. The CA LED (DCE Ready) must be on.
• Remote_Line (Loop C) -- Allows the DTE to check the functions of the
transmission path to the remote DCE interface.
Figure 5-2 illustrates how the DTE and DCE transmit loopback signals over
Local_Digital (Loop A), Local_Line (Loop B), and Remote_Line (Loop C).
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