Panasonic KX-TES - Manual (Page 57)

5. Communicating Within Your Office
DBS-32-755 Issued April 2000 55
The camp-on feature alerts you when a busy extension is free.
1. Pick up the handset or press ON/OFF.
2. Dial the extension number.
3. When you hear a busy tone, press 3.
4. When you hear a ringing tone, replace the handset or press ON/OFF.
Your extension rings when the busy extension becomes free.