Siemens Simatic S7 Series Manual page 47

Further Expansion. The.PLC.program.can.be.further.expanded.to.accommodate.a.
wide.variety.of.commercial.and.industrial.applications.
Start/Stop.pushbuttons,.selector.switches,.indicator.lights,.and.
signaling.columns.can.be.added..Motor.starters.can.be.added.
for.control.of.additional.motors..Over-travel.limit.switches.can.
be.added.along.with.proximity.switches.for.sensing.object.
position..Various.types.of.relays.can.be.added.to.expand.the.
variety.of.devices.being.controlled.
As.needed,.expansion.modules.can.be.added.to.further.
increase.the.I/O.capability..The.applications.are.only.limited.by.
the.number.of.I/Os.and.amount.of.memory.available.for.the.
PLC.
Signaling
Indicator Lights Relays Motor Starters
Column
Discrete Ouputs
SF/DIAG
Expansion Module
Discrete Inputs
Selector
Pushbuttons Limit Switches Proximity Switches
Switch
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