diff --git a/cpdctrl/led_control_device/__init__.py b/cpdctrl/led_control_device/__init__.py
index 20cf765..68c04d9 100644
--- a/cpdctrl/led_control_device/__init__.py
+++ b/cpdctrl/led_control_device/__init__.py
@@ -1 +1,25 @@
-from cpdctrl.led_control_device.base import LedControlDevice
\ No newline at end of file
+from cpdctrl.led_control_device.base import LedControlDevice
+from cpdctrl.led_control_device.impl.test import TestLedControlDevice
+
+
+def list_devices() -> dict[str,list[str]]:
+    devices = {
+        "TEST": ["Led Control Dummy Device"],
+    }
+    try:
+        from .impl import thorlabs_ledd1b as th
+        devices["ARDUINO"] = ["Thorlabs LEDD1B"] #keithley2700.enumerate_devices()
+    except ImportError:
+        pass
+    return devices
+
+def connect_device(typename: str, devicename: str) -> LedControlDevice:
+    if typename == "TEST":
+        return TestLedControlDevice()
+    elif typename == "ARDUINO":
+        try:
+            from .impl import thorlabs_ledd1b as th
+            return th.LEDD1B()
+        except ImportError as e:
+            raise ValueError(f"Arduino devices not available: {e}")
+    raise ValueError(f"Unknown device type {typename}")
\ No newline at end of file
diff --git a/cpdctrl/led_control_device/impl/test.py b/cpdctrl/led_control_device/impl/test.py
new file mode 100644
index 0000000..c64067d
--- /dev/null
+++ b/cpdctrl/led_control_device/impl/test.py
@@ -0,0 +1,14 @@
+from ..base import LedControlDevice
+
+class TestLedControlDevice(LedControlDevice):
+    def __init__(self):
+        super().__init__()
+
+    def on(self):
+        pass
+
+    def off(self):
+        pass
+
+    def set_level(level: int):
+        pass
diff --git a/cpdctrl/voltage_measurement_device/__init__.py b/cpdctrl/voltage_measurement_device/__init__.py
new file mode 100644
index 0000000..003cd95
--- /dev/null
+++ b/cpdctrl/voltage_measurement_device/__init__.py
@@ -0,0 +1,31 @@
+
+from .base import VoltageMeasurementDevice
+
+try:
+    from .impl.keithley2700 import Keithley2700
+except ImportError:
+    pass
+
+from .impl.test import TestVoltageMeasurementDevice
+
+def list_devices() -> dict[str,list[str]]:
+    devices = {
+        "TEST": ["Voltage Measurement Dummy Device"],
+    }
+    try:
+        from .impl import keithley2700
+        devices["VISA"] = ["example visa device"] #keithley2700.enumerate_devices()
+    except ImportError:
+        pass
+    return devices
+
+def connect_device(typename: str, devicename: str) -> VoltageMeasurementDevice:
+    if typename == "TEST":
+        return TestVoltageMeasurementDevice()
+    elif typename == "VISA":
+        try:
+            from .impl import keithley2700
+            return keithley2700.init(devicename)
+        except ImportError as e:
+            raise ValueError(f"VISA devices not available: {e}")
+    raise ValueError(f"Unknown device type {typename}")
\ No newline at end of file
diff --git a/cpdctrl/voltage_measurement_device/impl/test.py b/cpdctrl/voltage_measurement_device/impl/test.py
new file mode 100644
index 0000000..5797c1a
--- /dev/null
+++ b/cpdctrl/voltage_measurement_device/impl/test.py
@@ -0,0 +1,54 @@
+from ..base import VoltageMeasurementDevice
+from typing import Callable
+from time import time as now
+import numpy as np
+
+class TestVoltageMeasurementDevice(VoltageMeasurementDevice):
+    def __init__(self, ampltiude: float=1.0, frequency: float=3.0):
+        super().__init__()
+        self.amplitude = ampltiude
+        self.frequency = frequency
+        self.t0 = now()
+
+    # RUN COMMANDS ON THE DEVICE
+    def run(self, code, verbose=False):
+        pass
+
+    def run_script(self, script_path, verbose=False):
+        pass
+
+    def reset(self, verbose=False):
+        pass
+
+    def read_value(self) -> tuple[float, float]:
+        """
+        Read a single value
+
+        Returns
+        -------
+        [timestamp, voltage]
+        """
+        t = now() - self.t0
+        v = self.amplitude * np.sin(2 * np.pi * t / self.frequency)
+        return t, v
+
+    def measure(self, interval: int, update_func: Callable[None, [int, float, float]] | None = None,
+                max_measurements: int | None = None):
+        """
+        Take voltage readings after <interval> milliseconds.
+
+        Parameters
+        ----------
+        interval : int
+            Number of milliseconds to wait between readings.
+        update_func : Callable[None, [int, float, float]] or None, optional
+            A function that is called after each reading with parameters <n_reading>, <time>, <voltage>. The default is None.
+        max_measurements : int or None, optional
+            Number of readings to perform. Set to None for infinite. The default is None.
+
+        Returns
+        -------
+        None.
+
+        """
+        pass