HP 3438A Operating And Service Manual page 56

Section V l I I Model 3438A
4.6V REF.
CIFCUITRI
CONTROLLER
DISPLAY
INPUT
SWITCWING
c c u
;--
+ 5 v REF. IIREF.
I
I
+ 4 . 6 V REF.
Figure 8-1. Simplified Block Diagram.