IBM 1 Series Manual page 97

User's signal lines Timer card
Top-card connector
{
Timer X customer clock +5 V
or ——»>—__—+—(_)
Timer X external gate DI
TTL Filtered
jumpers TTL jumpers 4949
to V
+5.V
1502
One
@—> TTL
- load
3309 400 pf
Timer X signal ground | ©>-
+5 V
7502
Timer X external gate enable
or <~—__—__—_—_;+—_{()
Timer X run state DO oN
"Oo
Frame ground strap
(one only) / / /
Figure 3-2. Driver/receiver circuits on the timer card
3-4 =GA34-0033