diff --git a/simulations/03_emitter_receiver_simulation.ipynb b/simulations/03_emitter_receiver_simulation.ipynb
index 9210294..0f026a9 100644
--- a/simulations/03_emitter_receiver_simulation.ipynb
+++ b/simulations/03_emitter_receiver_simulation.ipynb
@@ -15,7 +15,12 @@
    "source": [
     "import numpy as np\n",
     "\n",
-    "import matplotlib.pyplot as plt"
+    "import matplotlib.pyplot as plt\n",
+    "\n",
+    "import os\n",
+    "import sys\n",
+    "# Append parent directory to import path so lib can be found\n",
+    "sys.path.append(os.path.dirname(os.path.abspath(os.getcwd())))"
    ]
   },
   {
diff --git a/simulations/04_recover_timing_errors.ipynb b/simulations/04_recover_timing_errors.ipynb
index 6e7359a..4e20076 100644
--- a/simulations/04_recover_timing_errors.ipynb
+++ b/simulations/04_recover_timing_errors.ipynb
@@ -50,7 +50,7 @@
     "def distance(x, y = emit_location):\n",
     "    return np.sqrt( np.sum((x - y)**2, axis=-1) )\n",
     "\n",
-    "actual_err_timings = rng.random(N)\n",
+    "actual_err_timings = 2 * rng.random(N) - 1\n",
     "if not True:\n",
     "    # undo timing errors\n",
     "    actual_err_timings = np.zeros_like(actual_err_timings)\n",
@@ -132,10 +132,11 @@
     "# plot\n",
     "if True:\n",
     "    fig, ax = plt.subplots()\n",
-    "    ax.plot(distance(locations, 0), actual_timings, 'o')\n",
-    "    ax.plot(distance(locations, 0), timings, 'o')\n",
+    "    ax.plot(distance(locations, 0), actual_timings, 'o', label='actual')\n",
+    "    ax.plot(distance(locations, 0), timings, 'o', label='with errors' )\n",
     "    ax.set_xlabel(\"Distance\")\n",
     "    ax.set_ylabel(\"Timing\")\n",
+    "    ax.legend()\n",
     "    plt.show();"
    ]
   },