diff --git a/Radio-operation.md b/Radio-operation.md
index 4da5f6d..3c83368 100644
--- a/Radio-operation.md
+++ b/Radio-operation.md
@@ -43,6 +43,10 @@ You can change the scan direction while scanning with `UP/DOWN` buttons.
 
 The scan can be stopped with the `EXIT` button, the search result will be ignored and frequency/channel will return to the one that was set before scan begun. Alternatively you can stop the scan with `PTT` or `MENU` button in which case the frequency/channel will be set to the last channel where transmission was found.
 
+# 1750 Hz toneburst for repeater access.
+When the `PTT` is pressed, the 1750 Hz can be activated by pressing `function key 2` (side key 2, bottom).
+
+
 # DTMF calling (decoding)
 
 [DTMF](https://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling) calling can be turned on in the menu `D Decd` (DTMF Decoding). You need a computer and programming cable to setup the whole system. You need to change `ANI ID` (programmable from the computer) of each radio to be unique in your network. It is also a good idea to program the list of contacts, their IDs and names.