Telos Zephyr Xstream User Manual page 291

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ISDN
This option causes two different things to happen.
a) Data coming in the ISDN interface (when INTERFACE is set to ISDN )
is sent back out the same channel(s) of the interface. Therefore, the
unit on the other end should be able to receive its own audio back
(assuming it is configured for compatible Transmit and Receive
modes). If this is the case, the network path is functioning.
b) Codec data from the encoder is passed back to the decoder (when
INTERFACE is set to ISDN). Therefore, you should receive your own
audio back (assuming it is configured for compatible Transmit and
Receive modes) with delay and quality dependant on the coding
mode used. This tests over 70% of the Xstream's functionality.
This mode can be used to audition the various coding modes even when no
ISDN circuit is present.
AUDIO LOOPBACK
SWITCHES
SEND
audio
OFF
A
ON
U
D
I
RCV
ON
O
OFF
audio
Xstream
The AUDIO and ISDN loopback modes are illustrated above. The
switches on the left side are activated for the AUDIO LOOPBACK
mode while the switches on the right are activated for the ISDN
LOOPBACK mode.
Section 13: Deep Tech Information and Troubleshooting
USER'S MANUAL
clk
ISDN LOOPBACK
SWITCHES
data
ENCODER
OFF
ON
IOFF ION
ON
OFF
data
DECODER
clk
TxC
TxD
ISDN
Interface
RxD
RxC
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