Ericsson DT400 User Manual page 86

Tones and Signals
Internal ringing signal
External ringing signal
Automatic call-back signal
86
Signals
Ringing signals are emitted from the phone..
Note: The tones and ringing signals in this guide refer to the
standard system but may vary between countries.
BusinessPhone – Cordless DT400/DT410/DT420/DT430
- repeated after 4 s
- repeated after 4 s