diff --git a/plots/01_tx_lines.py b/plots/01_tx_lines.py
index 2246895..1ee2bba 100644
--- a/plots/01_tx_lines.py
+++ b/plots/01_tx_lines.py
@@ -3,7 +3,7 @@ import logging
 
 import numpy as np
 from matplotlib import pyplot as plt
-from utils import AnimatedPlot, dir_assets
+from utils import AnimatedPlot, dir_assets, pi_ticks
 
 # %% logging
 log = logging.Logger(__name__)
@@ -68,19 +68,6 @@ class SuperpositionPlot(AnimatedPlot):
         self.ax.set_ylabel("V")
         self.ax.set_title(f"$t={t:0.2f}$")
 
-        def pi_ticks(value, tick_number):
-            # find number of multiples of pi/2
-            N = int(np.round(2 * value / np.pi))
-            if N == 0:
-                return "0"
-            elif np.abs(N) == 2:
-                # +/- 1 * pi
-                return "$" + ("-" if N < 0 else "") + r"\pi$"
-            elif N % 2 == 0:
-                return "$" + f"{N // 2}" + r"\pi$"
-            else:
-                return "$" + ("-" if N < 0 else "") + r"\frac{" + f"{np.abs(N)}" + r"}{2}\pi$"
-
         self.ax.xaxis.set_major_locator(plt.MultipleLocator(np.pi / 2))
         self.ax.xaxis.set_major_formatter(plt.FuncFormatter(pi_ticks))
         self.ax.grid(True)
@@ -91,11 +78,11 @@ class SuperpositionPlot(AnimatedPlot):
 class ReflectionPlot(AnimatedPlot):
     x = np.linspace(-4 * np.pi, 0, 500)
 
-    def __init__(self, zl: complex, **kwargs):
+    def __init__(self, zl: complex, z0: complex = 1 + 0j, **kwargs):
         super().__init__(**kwargs)
 
         self.zl = zl
-        self.z0 = 1
+        self.z0 = z0
 
     def update(self, t: float):
         v = 2 * np.pi
@@ -119,19 +106,6 @@ class ReflectionPlot(AnimatedPlot):
         self.ax.set_ylabel("V")
         self.ax.set_title(f"$Z_L/Z_0={self.zl}$, $t={t:0.2f}$")
 
-        def pi_ticks(value, tick_number):
-            # find number of multiples of pi/2
-            N = int(np.round(2 * value / np.pi))
-            if N == 0:
-                return "0"
-            elif np.abs(N) == 2:
-                # +/- 1 * pi
-                return "$" + ("-" if N < 0 else "") + r"\pi$"
-            elif N % 2 == 0:
-                return "$" + f"{N // 2}" + r"\pi$"
-            else:
-                return "$" + ("-" if N < 0 else "") + r"\frac{" + f"{np.abs(N)}" + r"}{2}\pi$"
-
         self.ax.xaxis.set_major_locator(plt.MultipleLocator(np.pi / 2))
         self.ax.xaxis.set_major_formatter(plt.FuncFormatter(pi_ticks))
         self.ax.grid(True)
diff --git a/plots/utils.py b/plots/utils.py
index 9f4e2ef..cf2b611 100644
--- a/plots/utils.py
+++ b/plots/utils.py
@@ -21,6 +21,20 @@ dir_assets = dir_root / "assets"
 
 
 # %%
+def pi_ticks(value, tick_number):
+    # find number of multiples of pi/2
+    N = int(np.round(2 * value / np.pi))
+    if N == 0:
+        return "0"
+    elif np.abs(N) == 2:
+        # +/- 1 * pi
+        return "$" + ("-" if N < 0 else "") + r"\pi$"
+    elif N % 2 == 0:
+        return "$" + f"{N // 2}" + r"\pi$"
+    else:
+        return "$" + ("-" if N < 0 else "") + r"\frac{" + f"{np.abs(N)}" + r"}{2}\pi$"
+
+
 class AnimatedPlot(ABC):
     fig: Figure
     ax: Union[Axes, Tuple[Axes]]