Tektronix 2221A, User Manual

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1. VARHOLDOFF
(Variable Holdoff) —- Varies the amount of time the horizontal system waits
before beginning another sweep. This helps stabilize the display of some
waveforms.
The holdoff time in the MAX position is at least 10 times greater than NORM.
2. P-P AUTO/TV LINE
Automatically determines the trigger level on repetitive signals of 20 Hz and
higher in NON-STORE and 500 Hz and higher in STORE. Initiates a base­
line reference trace in the absence of an adequate trigger signal.
If a TV signal is applied, the oscilloscope will trigger on the TV line informa­
tion.
3. NORM
(Normal Triggering Mode) — In NON-STORE, the TRIGGER LEVEL control
sets the trigger point regardless of the trigger signal amplitude. The oscillo­
scope does not automatically sweep without an adequate trigger signal.
This mode is useful for low frequency or iow repetition rate signals.
In STORE, the last signal acquired is displayed until the next trigger occurs.
TV FIELD — (Press P-P AUTO and NORM in at the same time.) This mode
sets the oscilloscope to trigger on television field (vertical sync) signals. The
A sweep will occur automatically in the absence of a trigger signal,
4. EXT COUPL
Selects the method of coupling the EXT INPUT signal:
AC — Capacitively couples (and blocks DC components) of the signal.
DC — Couples DC and all other signal components.
DC/10 — Couples all signal components and attenuates the external input
signal by a factor of 10.
5. EXT INPUT
Input connection for an externa! trigger signal.
2221A User Manual
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