Model 
3720A 
1. 
2. 
3. 
4. 
5. 
2 
1 
27  26  25 
28 
29 
30 
3 
4 
5 
6 
7 
8 
9 
10 
1'1 
1'2 
13 
14 
1'5 
16 
ii 
is 
21 
31 
24 
23 
22 
DISPLAY: 
8 
y 
10 division  CRT,  with  graticule 
calibrated 
in 
one  division squares.  Major  axes  cali- 
brated 
in 
0.2 
division intervals. 
1 
division 
= 
0.95cm. 
6. 
STORAGE  TIME: 
potentiometer. Varies  the time 
any  display is stored,  when 
in 
STORE mode. 
DISPLAY SENSITIVITY: 
illuminated digital readout. 
Scales  the  horizontal  and  vertical  axes and the fre- 
quency  ..interval, 
Af, 
as  selected  by  Scale  Factor 
switch. 
SCALE  FACTOR: 
lever  switch.  Selects  axis calibra- 
tion to be presented  on the Display Sensitivity  panel. 
ERASE: 
pushbutton.  Eradicates  all  traces  displayed 
on storage  CRT screen,  when  not 
in 
STORE  mode. 
INTENSITY: 
potentiometer.  Controls  brightness  of 
CRT 
beam. 
7. 
8. 
9. 
10. 
FOCUS: 
potentiometer.  Adjusts  sharpness  of  CRT 
beam. 
PERSISTENCE: 
potentiometer.  Controls duration of 
written  trace,  when  not 
in 
STORE  mode.  Fully 
clockwise position selects STORE mode. 
INPUT: 
lever  switch.  Routes  data  from the 3721A 
into Store 1 or 
2 
as selected. 
In 
HOLD 
position retains 
data 
in 
stores. 
LINE-ON: 
toggle  switch.  Controls ac  supply  to 
the 
instrument. 
Figure 
1-2 
Front panel controls and indicators 
L 
1-2 
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