IBM Series 1 User Manual page 119

Figure 3-2. Driver/receiver circuits on
the timer
card
User's signal lines
Timer card
Top-card connector
I
Tim:: X customer clock
(--+---11--<
TImer X external gate \ DJ
TTL
Filtered
+5 V
Timer
X
signal ground
400PF
9
+5 V
750
n
or ~------~~~--------------------------~ __ --~
Timer X external gate enable!
Timer X run state
DO
3-12
Frame ground strap
(one only)
GA34-0033
+5 V
1 TTL
load
(
. .