Siemens Simatic S7 Series Manual page 54

In.the.following.timer.example,.when.input.I0.3.turns.on,.the.
I0.3.contact.closes,.and.timer.T37.begins.timing..T37.has.a.time.
base.of.00.ms.(0..seconds)..The.preset.time.(PT).value.has.
been.set.to.50..Because.the.resolution.of.the.timer.is.set.to.
00.ms,.a.preset.value.of.50.is.equal.to.5.seconds.(50.x.00.
ms)..Therefore,.5.seconds.after.the.I0.3.contact.closes,.timer.
bit.T37.becomes.a.logic.,.the.T37.contact.closes,.and.output.
coil.Q0..and.its.associated.output.point.turn.on.
If.the.switch.opens.before.5.seconds.has.elapsed,.the.
accumulate.time.resets.to.0..Because.this.type.of.timer.does.
not.retain.its.accumulated.time.when.its.input.(IN).goes.to.logic.
0,.it.is.said.to.be.non-retentive.
Network 1
I0.3
Network 2
T37
53
T37
TON
IN
100 ms
PT
+150
Preset time = 150 x 100 ms = 15 seconds
Q0.1