Siemens SIMATIC S7-200 - Basic Ladder Logic Symbols

Installing an S7-200 PLC
2-15
S7-200 Programmable Controller System Manual
A5E00066097-02
L1
N
PE
[a]
DO
DI
PS
S7-200
DC/DC/DC
DO
EM 222
DC
DI
EM 221
DC
[e]
[g]
[b]
[c]
[d]
[f]
L+ M
24 VDC
AC
DC
[h]
Floating [f] or Grounded [g]
M
Figure 2-12 DC System Installation