Panasonic KX-TD500 System Reference Manual page 594

4.00 Automatic Callback
4.01 Automatic Callback-Trunk
Description
When calling an outside party and an idle line is
not available, the extension will be called back
when a CO line becomes available. The
extension can seize a CO line only by off-
hooking.
We call this function "Callback-Trunk". "Callback-
Trunk" has 2 types.
1. When seizing a CO line, it checks whether a
CO line is idle or not. If no line is available, a
busy tone is sent. Once a CO line is available,
the extension will be called back.
(If the telephone goes off-hook before the
callback is received, callback is cancelled and
you will hear a dial tone.)
2. After receiving all of the outside calls, it checks
whether an idle CO line is available or not. If
there is no idle line, you will hear a busy tone.
As soon as a CO line becomes idle, it will be
seized. Once the extension is off-hook, the last
number dialed is sent and you will hear the CO
line ring.
Type 1 is the default.
Each type can be set to a trunk group by the
dumb command "CAI". This function can activate
extensions that are set to "Yes" in the "Automatic
callback-Trunk" of Station (1/4).
Programming
System Programming
"Extension-Station (1/4)",
Automatic Callback-Trunk
"CO Access Instantly"
Conditions
If the telephone is off-hook before callback
ringing starts, this feature is cancelled.
A maximum of 64 extensions are able to callback
at the same time.
The following features can also be accessed:
• Local CO line Access
• Trunk Group 01-48 Access
• Calling by CO button (Private CO, Single
CO, Group CO) in the hands-free mode.
5-A-14
Reference
VT Dumb
10-G-1.01 11-C-24.00