Agilent Technologies 83491, Руководство пользователя, Страница: 20 / 68

2-6
Operation
Front-Panel Features
SELECT
key Pressing this key changes the modulation rate of the input signal. The recov-
ered and retimed clock trigger is sent to the mainframe. The
Trigger On Data
selection is a bypass mode where the data stream directly triggers the main-
frame.
Refer to “Block Diagrams” on page 2-8 to view a schematic of the nor-
mal and bypass paths.
UNLOCKED
indicator
83491/2/3A
This light shows when clock recovery cannot be established on the signal. If a
clock rate is selected, the trigger output to the mainframe
is disabled to pre-
vent free-run triggering. However in bypass mode (
Trigger On Data
selected),
triggering is not disabled. When the
UNLOCKED
light is on, you can establish a
trigger on the data input to the reference receiver.
Trigger Loss
indicator
83494A This light shows when clock recovery cannot be established on the signal. If a
clock rate is selected, the trigger output to the mainframe
is disabled to pre-
vent free-run triggering. However in bypass mode (
Trigger On Data
selected),
triggering is not disabled. When the
Trigger Loss
light is on, you can establish a
trigger on the data input to the reference receiver.
Auxiliary outputs
DATA
connector: This connector provides a fully regenerated version of the
input signal. It is intended for monitoring purposes only and not for rigorous
eye mask compliance testing. The frequency response does not conform to the
requirements for eye mask testing as described in ITU-T G.957 and Bellcore
GR-253-CORE. On Agilent 83492A and 83493A modules, this port is ampli-
tude stabilized for input signals greater than approximately –23 dBm. On
Agilent 83494A modules, this port is amplitude stabilized for input signals
greater than approximately –10 dBm.
Green and red data-rate lights
The data-rate indicator lights on the Agilent 83491/2/3A and Agilent 83494A Option 106
change color between red and green to show which data rate is selected. A red light
does
not indicate a problem. A red light shows that the adjacent red data rate label is
selected. A green light shows that the adjacent green data rate label is selected.
Repeatedly pressing the SELECT key cycles through the selections in one color before
switching to the opposite color. On Agilent 83491A modules for example, the first selec-
tion cycle shows 155 Mb/s selected. The second selection cycle shows 1062 Mb/s
selected.
Agilent 83494A modules use only the green data-rate indicator light to show which data
rate is selected. Repeatedly pressing the SELECT key cycles through the available data
rates, as well as the Trigger On Data bypass mode.
book.book Page 6 Monday, January 7, 2002 2:12 PM