Tektronix 475A - Page 17

NORM: Sweep is initiated by the applied trigger signal.
In the absence of an adequate trigger signal, there is no
trace. When the trigger rate is too low for AUTO use
NORM.
SINGL SWP: When this pushbutton is pushed, the A
Sweep operates in the single sweep mode. After a single
sweep is displayed, further sweeps cannot be presented
until the SINGLE SWP button is again pushed. It is useful
when the signal to be displayed is not repetitive or varies in
amplitude, shape or time causing an unstable conven-
tional display. It can aiso be used to photograph a
nonrepetitive signal.
26. READY Lamp--indicates A Sweep is “armed” and,
upon receipt of an adequate trigger signal, will present a
single-sweep display.
27. TRIG Lamp--indicates that A Sweep is triggered
and will produce a stable display. It is useful for setting up
the trigger circuits when a trigger signal is available
without a display on the crt (for example, when using
external triggers).
28. A TRIG HOLDOFF—Provides continuous control
of time between sweeps. Allows triggering on aperiodic
signals (such as complex digital words). In the fully
clockwise position (B ENDS A), A sweep is reset at the end
of B sweep to provide the fastest possible sweep repetition
@
i
475A/DM44
Operators
rate for delayed-sweep presentations and low-repetition
rate signals. Use the A trigger controls for the best
possible display before using the A TRIG HOLDOFF
control.
29. COUPLING—Determines method used to couple
signals to the trigger generator circuit.
AC: Signals are capacitively coupled to the input ofthe
trigger generator, Dc is rejected and signals below about
60 Hz are attenuated.
LF REJ: Signals are capacitively coupled to the input
of the trigger circuit. Dc is rejected and signals below
about 50 kHz are attenuated. It is useful for providing a
stable display of the high-frequency components of a
complex waveform.
HF REJ: Signals are capacitively coupled to the input
of the trigger circuit. Dc is rejected and signals below
about 60 Hz and above about 50 kHz are attenuated. It is
useful for providing a stable display of the low-frequency
components of a complex waveform.
DC: AH components of a trigger signal are coupled to
the input of the trigger circuit. It is useful for providing a
stable display of low-frequency or low-repetition rate
signals, except the combination of the ALT (dual trace)
mode with the trigger SOURCE switch in NORM.