Anritsu MG3641A - Manual (Page 67)

SECTION 4 OPERATING INSTRUCTIONS
For the external modulation input, you can select either DC coupling or AC coupling by following the procedure
detailed below:
(1) Press the "Src" [F4] key in the Modulation menu to open
the "Audio Source" menu.
(2) Select coupling display for Ext1 or Ext2 by operating
the "
↓" [F2], "↑" [F3], and "→" [F4] keys (the characters
are highlighted).
(3) Press the "Sel" [F1] key to change the setting.
Applying a signal at a voltage higher than
±10 V to the "Ext1" or "Ext2" connector could result in breakdown
of the unit. Be careful to prevent a signal level outside the limits from entering the unit.
CAUTION
Ω
1
3
3 2