Telos ZephyrExpress - Manual (Page 148)

9-6 TROUBLESHOOTING
this way, you’ve probably got a software problem... but there’s a possibility something
has gone wrong with the hardware.
If the LEDs light up but you can’t see any text on the LCD display, the most probable
cause is that someone left the backlighting or contrast at an inappropriate setting.
p
Press the DROP button and hold that button in while turning the EDIT knob clockwise to
reset the backlighting. It may take a few turns.
d
Press the DIAL button and hold that button in while turning the EDIT knob either direc-
tion to change the LCD Contrast.
NT1 status LED
North American ZephyrExpress units, with built-in NT1s, have a green LED on the back
of the unit next to the
LINE DIRECT jack. It should be steadily lit.
Rapid flashing means there’s no ISDN continuity. Check the line. Be sure it’s plugged
into the lower ZephyrExpress jack.
Slow flashing is normal when the connection is being established. If the LED continues
to flash slowly, check the SPIDs and switch type. And don’t automatically assume the
numbers that the telco installer gave you are correct.
LOOPBACK modes
You can check ZephyrExpress’ audio circuits by looping the send bus directly into the re-
ceive bus, check its coding operation by looping the transmit encoder directly into its re-
ceive encoder, or check the entire unit by dialing into another Zephyr or ZephyrExpress
that’s set to loop an incoming signal directly back.
Far Loopback for local audio testing
Set Codec: Loop mode to Far to connect ZephyrExpress’ send mixer directly to the receive
bus. The loopbackcircuit looks like the drawing on the next page.
Using Far Loopback and the block diagram, you should be able to trace an audio signal
through ZephyrExpress.
When using Far Loopback for local audio testing, the ISDN line doesn’t need to be active
and the transmit and receive coding methods don’t have to match.
w
IMPORTANT!
ZephyrExpress’ volume meters are driven by the audio codec. For this reason,
they’re disconnected during Far Loopback mode.