Keithley 3940 Operator's Manual page 29

SECTION3
Operation
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signal will be identical to the output during FCTN
OUT ON, but the sub synthesizer SYNC OUT sig-
nal will be set to high or low logic levels.
The liquid crystal display will indicate "OFF" in
the upper left corner when the Model 3940 is in the
FCTN OUT OFF mode (except in the SHIFT, SUB
or REMOTE modes).
Note that the factory default setting for FCTN
OUT is ON at power on.
MAIN SYNTHESIZER FCTN OUT @fain syn-
t~~siz~r~wavEforr;zoutlrut}
This BNC jack provides the main synthesizer
waveform output signal. The maximum output
voltage range is rtlOV/no load, and the output im-
pedance is 50B
MAIN SYNTHESIZER SYNC OUT (Main syn-
thesizer synchronous output)
This BNC jack provides a TTL-level square wave
signal at the same frequency as the main synthe-
sizer function output waveform. The output im-
pedance is approximately 5OQ and it can be use
with 5OQ terminations.
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SUB SYNTHESIZER FCTN OUT (Sub synthe-
sizer waveform output)
This BNC jack provides the sub synthesizer
waveform output signal. The maximum output
voltage range is rtlOV/no load, and the output im-
pedance is 600!2.
SUB SYNTHESIZER SYNC OUT (Sub synthe-
sizer synchronous output)
This BNC jack is the sub synthesizer synchronous
output, which outputs a TTL-level square wave
signal at the sub synthesizer output frequency.
EXT TRIG IN (External-trigger input)
This BNC connector is an input for external TTL-
level signals, which can be used to trigger the
Model 3940.
EXT TRIG IN is internally pulled up to a high logic
level, which means that the external trigger input
will remain high with no input signal connected. If
the EXTJ trigger source is selected with the unit
in the gate oscillation mode, the gate signal will be
enabled, and the unit will effectively be in the con-
tinuous i)scillation mode with no external trigger
input signal applied.
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