diff --git a/APSCT_I2C.py b/APSCT_I2C.py
index 3ac297b281d38a6aa7f8264db1e8b5d534e3e736..1715b6fb8345e2d9b8e37b8bae309833fe36e3a9 100644
--- a/APSCT_I2C.py
+++ b/APSCT_I2C.py
@@ -59,3 +59,8 @@ PLL_160M = 0x21
 # Central I2C Devices
 #
 EEPROM = 0x50
+
+#
+# I2C switch addresses
+#
+i2c_switch_addr = [0x70, 0x71, 0x72, 0x73]