Grandstream Networks HT813 Administration Manual page 52

In certain countries, the central office will send a special busy tone to indicate when a call is disconnected
from the remote side. User can pre-configure this tone on the ATA. The user should know the frequency
values and cadences of these tones.
Here is an example for the syntax for a busy tone in the U.S.A:
PSTN
Disconnect
Syntax: f1=freq@vol, f2=freq@vol, c=on1/off1-on2/off2-on3/off3;
Tone
Note: freq: 0 – 4000Hz; vol: -30 – 0dBm
Default: Busy Tone – f1=480@-32, f2=620@-32, c=500/500;
Note: Maximum supported cadences are 3
This should be set to Yes only if the FXO lines are subscribed to PR service from PSTN Service provider. It
is merely a PR detect feature. Default is No.
Enable
Polarity
Note: If there is no PR service from provider on the FXO line, and this setting is
Reversal
configured to Yes, calls will not be successful.
AC
You can select the AC termination by Country or by Impedance.
Termination
Model Default is Country-based.
15 Countries are selectable in this version of the F/W.
USA
AUSTRIA
AUSTRALIA/NEW ZEALAND
BELGIUM
CHINA
FINLAND
FRANCE
Country-
GERMANY
Based
GREECE
ITALY
JAPAN
NORWAY
SPAIN
SWEDEN
UK
Default is USA