diff --git a/defines.h b/defines.h
index 7982f2c..2d48809 100644
--- a/defines.h
+++ b/defines.h
@@ -15,6 +15,8 @@
 #define CONFIG_SWITCH 4
 #define LED_PIN 14
 
+// These both pins are connected via a 470k resistor.
+// The insulated touchpad is connected to pin TOUCH_PIN_RECEIVE.
 #define TOUCH_PIN_RECEIVE 16
 #define TOUCH_PIN_SEND 5