Telos ZephyrExpress Loopback modes, TheyÕre disconnected during Far Loopback mode, NT1 status LED

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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.

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.

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.

wWhen 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.IMPORTANT!ZephyrExpressÕ volume meters are driven by the audio codec. For this reason,

theyÕre disconnected during Far Loopback mode.

9-6 TROUBLESHOOTING