diff --git a/artiq/sim/devices.py b/artiq/sim/devices.py
index 65e814eb9..cb0e49e79 100644
--- a/artiq/sim/devices.py
+++ b/artiq/sim/devices.py
@@ -1,5 +1,6 @@
 from random import Random
 
+from artiq.language.core import MPO, delay
 from artiq.language import units
 from artiq.sim import time
 
@@ -7,37 +8,32 @@ class Core:
 	def run(self, k_function, k_args, k_kwargs):
 		return k_function(*k_args, **k_kwargs)
 
-class Input:
-	def __init__(self, name, prng_seed=None, wait_max=20, count_max=100, wait_min=0, count_min=0):
-		self.name = name
-		self.wait_min = wait_min
-		self.wait_max = wait_max
-		self.count_min = count_min
-		self.count_max = count_max
-		self.prng = Random(prng_seed)
+class Input(MPO):
+	parameters = "name"
+
+	def build(self):
+		self.prng = Random()
 
 	def wait_edge(self):
-		duration = self.prng.randrange(self.wait_min, self.wait_max)*units.ms
+		duration = self.prng.randrange(0, 20)*units.ms
 		time.manager.event(("wait_edge", self.name, duration))
-		time.manager.take_time(duration)
+		delay(duration)
 
 	def count_gate(self, duration):
-		result = self.prng.randrange(self.count_min, self.count_max)
+		result = self.prng.randrange(0, 100)
 		time.manager.event(("count_gate", self.name, duration, result))
-		time.manager.take_time(duration)
+		delay(duration)
 		return result
 
-class WaveOutput:
-	def __init__(self, name):
-		self.name = name
+class WaveOutput(MPO):
+	parameters = "name"
 
 	def pulse(self, frequency, duration):
 		time.manager.event(("pulse", self.name, frequency, duration))
-		time.manager.take_time(duration)
+		delay(duration)
 
-class VoltageOutput:
-	def __init__(self, name):
-		self.name = name
+class VoltageOutput(MPO):
+	parameters = "name"
 
 	def set(self, value):
 		time.manager.event(("set_voltage", self.name, value))
diff --git a/examples/simple_simulation.py b/examples/simple_simulation.py
index d44a93af6..d60b26f5d 100644
--- a/examples/simple_simulation.py
+++ b/examples/simple_simulation.py
@@ -18,12 +18,13 @@ if __name__ == "__main__":
 	from artiq.sim import devices as sd
 	from artiq.sim import time
 
+	coredev = sd.Core()
 	exp = SimpleSimulation(
-		core=sd.Core(),
-		a=sd.WaveOutput("a"),
-		b=sd.WaveOutput("b"),
-		c=sd.WaveOutput("c"),
-		d=sd.WaveOutput("d"),
+		core=coredev,
+		a=sd.WaveOutput(core=coredev, name="a"),
+		b=sd.WaveOutput(core=coredev, name="b"),
+		c=sd.WaveOutput(core=coredev, name="c"),
+		d=sd.WaveOutput(core=coredev, name="d"),
 	)
 	exp.run()
 	print(time.manager.format_timeline())