Operating
Instructions—7A42
CH1,
CH2, CH3, CH4.
In
the
PROG
CHAN
mode
the
CH1, CH2, CH3,
and
CH4
pushbuttons
are
used
to
select
and
indicate
the
channel
which
will
respond
to
the
TTL/ECL,
VOLTS/DIV,
GND, 1MΩ/50Ω,
DISPLAY
and
THRESH pushbutton
controls.
DISPLAY.
The
DISPLAY
pushbutton
turns
the
selected
channel
display
on
or
off.
In
the off
position
the
trace
is removed from
the
crt
display.
However,
the
signal
applied
to
that
channel
is
still
routed
to
the
TRIGGER
FUNCTION
circuitry,
providing
the
channel
GND
indicator
is
not
lit.
TTL/ECL.
The
TTL/ECL
pushbutton
offers
a
threshold
range
and
selection
of
display
sensitivities
appropriate
for
either
TTL
or
ECL
logic
families.
VOLTS/DIV.
The
VOLTS/DIV
pushbuttons
set
the
scale factor
of the
selected
channel.
The
scale
factor
is
displayed
on
the
mainframe
crt
readout;
refer
to
CRT
Readout
in
this
section.
Three
sensitivities
are
available
in
each
logic
family;
see
Table
2-4.
To
increase
the
sensitivity
(display
size)
press
the
upper
button.
TABLE
2-4
Channel
Volts/DIvislon Ranges
Logic
Family
At The BNC
Through
a 10X
Probe
TTL
(CMOS)
.1,
.2,
.5
V/Div
1,
2,
5
V/Div
ECL
20,
50,
100
mV/Div
.2,
.5,
1
V/Div
GND.
The
GND
pushbutton
connects
the
selected
channel
amplifier
input
to
ground
as a
reference
for
trace
positioning.
However,
the
incoming
signal
is
not
grounded;
it
is
disconnected from
the
amplifier
input.
1MΩ/50Ω.
The
1MΩ/50Ω
pushbutton
selects
the
input impedance
of
the
selected
channel.
The
available
impedances
are
1
megohm in parallel
with
about
15
pF,
or
50
ohms.
THRESH.
Each
of
the
four
input
channels
have
two
possible
preset
threshold
voltages,
+1.4 volts
for
the
TTL
mode
and
-1.30
volts
for
the
ECL
mode.
In
addition,
these
threshold
voltages
can
be
altered
using
the
LEVEL-0-
or
LEVEL-0-
pushbuttons.
The
SWITCHING THRESHOLD
VOLTS
display
will
indicate
the
threshold
voltage
present
at
each
of the
channel
inputs.
To
turn
the
SWITCHING
THRESHOLD
VOLTS
display
on,
press
the THRESH
pushbutton
(the
light
should
be
on).
The
SWITCHING
THRESHOLD
VOLTS
display
corresponds
to
the
channel
pushbutton
that
is
lit
(CH1, CH2, CH3,
or
CH4).
While
the
button
is
lit,
the
actual
threshold
voltage
for
the
channel
is
indicated
in
the
seven-segment
LED display.
For
each
logic
family
there
are
internally
preset
thresholds
that
can
be
altered by
pressing
either
the
LEVEL
O
or
LEVEL-C-
button.
A
single
push
changes
the
threshold
by
one
increment.
When
either
LEVEL
button
is
held
down the
rate
2-65