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Triggering on Waveforms
3–112
TDS 500C, TDS 600B, & TDS 700C User Manual
11. Press Level (main) ➞ Level, Set to TTL, Set to ECL, or Set to 50% (side).
Level lets you enter the delayed trigger level using the general purpose knob
or the keypad.
Set to TTL fixes the trigger level at +1.4 V.
Set to ECL fixes the trigger level at –1.3 V.
Set to 50% fixes the delayed trigger level to 50% of the peak-to-peak value
of the delayed trigger source signal.
NOTE. When you set the Vertical SCALE smaller than 200 mV, the oscilloscope
reduces the Set to TTL or Set to ECL trigger levels below standard TTL and
ECL levels. That happens because the trigger level range is fixed at ±12
divisions from the center. At 100 mV (the next smaller setting after 200 mV) the
trigger range is ±1.2 V which is smaller than the typical TTL (+1.4 V) or ECL
(–1.3 V) level.