Panasonic KX-TD500 System Reference Manual page 592

3.03 Busy Station Signaling (BSS)
Description
When the called PITS extension user is busy
talking on a DN or CO button, and the DN button
is idle, Busy Station Signaling informs the other
PITS extension user that he or she is called by
another extension with the flashing DN button.
The called extension user's telephone must be
off-hook.
To activate this function, assign "System-Class of
Service", BSS/OHCA to "Yes".
Programming
System Programming
"System-Class of Service (1/3)",
BSS/OHCA
Conditions
Busy Station Signaling is ineffective if the called
extension is preset to either of the following
functions:
• "System-Class of Service", BSS/OHCA
Deny is set to "Yes".
• "System-Class of Service", Call Forwarding/
Do Not Disturb is set to "Yes".
Operation
Calling an extension
1. Lift the handset.
• You hear dial tone 1, 3, or 4 .
2. Dial the directory number of the
other extension.
• You hear busy tone.
3. Dial " 3 ".
• You hear ringback tone.
• The indicator on the DN button
of the other station flashes in
240 wink.
Reference
VT Dumb
10-D-4.01 11-C-7.00
5-A-12