diff --git a/protocol.md b/protocol.md
index b671c44..9c9dc31 100644
--- a/protocol.md
+++ b/protocol.md
@@ -10,7 +10,7 @@ Eufy RoboVac 11s IR protocol
 |Logical 1 |  400µs | 1.6ms |
 |  Trailer |  400µs |  20ms |
 
-No carrier modulation.
+Carrier frequency: 38kHz
 
 Frame: (Preamble + 48bits + Trailer) * 3