diff --git a/LM75AD.md b/LM75AD.md
index 3c98f2c1..5eec08a5 100644
--- a/LM75AD.md
+++ b/LM75AD.md
@@ -29,6 +29,8 @@ Can also be used standalone if soldered to a board given the diagram is used
 
 ![Circuit](https://github.com/andrethomas/images/raw/master/lm75ad/SimpleCircuit.png)
 
+R1 and R2 are pull-up resistors which are required by the I2C bus to operate properly. If you have other I2C sensors with pull-up resistors connected to the same I2C bus it's probably not necessary to have them.
+
 ### Hardware Configuration
 
 For connection to the ESP8266 I2C bus it is important to connect the SCL and SDA pins according to how the Sonoff firmware was configured.