diff --git a/docs/EN/supported_heating_systems.md b/docs/EN/supported_heating_systems.md
index 88f534b9..ca4ab5bc 100644
--- a/docs/EN/supported_heating_systems.md
+++ b/docs/EN/supported_heating_systems.md
@@ -16,7 +16,7 @@ Here are a few examples from heating controllers and the connectors that are use
 |[](){#RVP54}**RVP54** |<img src="../images/RVP54.jpeg">|PPS connection: A6/M|
 |[](){#RVS13}**RVS13** |<img src="../images/RVS13.jpeg">|BSB connection: CL+/CL-|
 |[](){#RVS21}**RVS21** |<img src="../images/RVS21.jpeg">|BSB connection via connector X86<br>**+** = rightmost pin<BR>**-** = second pin from right|
-|[](){#RVS21-AVS55}**RVS21 with AVS55** |<img src="../images/RVS21-AVS55.jpeg">|AVS55 extension module, sitting on top of RVS21.<br>BSB connection via connector X86:<br>**+** = rightmost pin<BR>**-** = second pin from right|
+|[](){#RVS21-AVS55}**RVS21 with AVS55** |<img src="../images/RVS21-AVS55.jpeg">|AVS55 extension module, sitting on top of RVS21.<br>BSB connection either via connector X86:<br>**+** = rightmost pin<BR>**-** = second pin from right<br>or via connector X150:<br>**+** = topmost pin<BR>**-** = second pin from top|
 |[](){#RVS23}**RVS23** |<img src="../images/RVS23.jpeg">|LPB connection: LPB/M|
 |[](){#RVS41}**RVS41** |<img src="../images/RVS41.jpeg">|BSB connection: CL+/CL-<br>LPB connection: MB/DB|
 |[](){#RVS43}**RVS43<br>LOGON B**|<img src="../images/RVS43.jpeg">|BSB connection: CL+/CL-<br>LPB connection: MB/DB|